Conscious learning becomes unconscious knowledge
This unit is focused on basic maternal and fetai anatomical and physiological facts related to vaginal delivery. Precise and clear concept of these facts and their clinical application is must for obstetrician. Labor room management and record keeping an integral part of obstetrics, is also included in this unit.2
Unit Outlines
- 1.1. Maternal Passage—Pelvis
- 1.2. Passenger—Fetal Dimensions and Dispositions
- 1.3. Movement of Passenger—Mechanism of Vaginal Delivery
- 1.4. Stages of Labor
- 1.5. Places of Vaginal Delivery—Labor Room
- 1.6. Record Keeping in Labor Management
Pelvic girdle is the bony ring through which body weight is transmitted to the lower extremities. In women it is adapted for specialized function of child bearing.
Pelvic girdle is the most variable part of the skeleton, depending on racial, sexual, evolutionary and developmental influences. Obstetrical significance of these variations in size, shape and dimension of pelvic girdle was first studied and classified by Caldwell and Moloy in 1933,1 and it helped in understanding various anatomical facts of obstetric significance.
So first let us revise the obstetrical anatomy of typical female pelvis.
False pelvis Lies above the linea terminalis. It is bounded posteriorly by lumbar vertebra, laterally by iliac fossa, in front by lower portion of anterior abdominal wall.
True pelvis It is important portion of pelvis for child bearing, which is bounded above by promontory and alae of sacrum, linea terminalis, and the upper margin of the pubic bones and below by pelvic outlet (Fig. 1.1.1).
Cavity of true pelvis can be described as an obliquely truncated bent cylinder with its greatest height posteriorly.
Planes and Diameter of True Pelvis
The pelvis is described having four imaginary planes:
1. Plane of pelvic inlet (brim) | - Superior strait (upper strait) |
2. Plane of pelvic outlet | - Inferior strait |
3. Plane of mid pelvis | - Least pelvic dimensions |
4. Plane of greatest pelvic dimension that has no obstetrical significance. |
Pelvic Inlet (Brim)
It is plane of division between the false and true pelvis. It is bounded posteriorly by sacral promontory, alae of sacrum, laterally by linea terminalis, and anteriorly by horizontal pubic rami and symphysis pubis.4
It has nearly round shape in gynecoid pelvis.
Diameters of Pelvic Inlet
- Anteroposterior diameter or obstetric conjugate It is measured from center of sacral promontory behind to nearest point in the middle line upon the posterior surface of symphysis pubis in front. Normally this measures 10 cm or more (Fig. 1.1.2—a, b).
- Transverse diameter It is constructed at right angle to obstetric conjugate, intersecting obstetrical conjugate at a point about 4 cm in front of promontory. Segment of obstetrical conjugate from intersection of these two lines to the promontory is designated the post-sagittal diameter of inlet (Fig. 1.1.2—g, h).
- Two oblique diameter are measured from sacroiliac articulation behind to ileopectineal eminence on the opposite side in front—Right oblique from right sacroiliac articulation to left ileopectineal eminence and left from left sacroiliac articulation to right ileopectineal eminence, measuring of average less than 13 cm (Fig. 1.1.2—c, d, e, f).5
Fig. 1.1.2: The female pelvis—diameters of inlet (ab—AP diameter, cd—Right oblique diameter, ef—Left oblique diameter, gh—Transverse diameter)
Clinical Significance
True conjugate that is anteroposterior diameter of pelvic inlet is not the shortest distance between promontory of sacrum and symphysis pubis.
Obstetric conjugate is shortest anteroposterior diameter through which the head must pass in descending through pelvic inlet. Clinically obstetric conjugate cannot be measured by examining fingers.6
So for clinical purpose it is estimated indirectly by first measuring “Diagonal Conjugate” which is determined by first measuring distance from lower margin of symphysis to the promontory of sacrum and then subtracting 1.5 to 2 cm from diagonal conjugate (Fig. 1.1.3).
Mid Pelvis—Pelvic Cavity
It is the space between the plane of brim above and the plane of outlet below. It forms a curved canal with shallow anterior wall (3.75 cm) and deep posterior wall (11.25 cm), and 7.5 cm deep lateral wall.7
Mid Plane
Plane of widest pelvic dimension: It is bounded in front by center of symphysis pubis and behind by junction of 2nd and 3rd sacral vertebra.
Pelvic Outlet
Anatomical outlet: It is a lozenge shaped area, consist of two approximately triangular areas, that are not in the same plane, having common base of imaginary line drawn between two ischial tuberosities (Fig. 1.1.4A).
Obstetrical outlet: It has certain characteristics which play an important role in mechanism of vaginal delivery and obstetric management. These are as follows:
- It is a shallow segment of pelvic cavity with lateral wall made up of greater part of ischial bones and posterior wall made up of coccyx. Its anterior wall is defective at pubic arch.
- Anteroposterior diameter of obstetric outlet: It is measured from center of lower border of the symphysis to tip of last sacral vertebra.
- Transverse diameter of obstetric outlet is between ischial spines. Oblique diameter can not be defined as between ischial tuberosities and coccygeal border the pelvic outlet is filled in with soft structure.
Plane of Least Pelvic Dimension—(Lower Pelvic Strait/Obstetrical Outlet/Narrow Pelvic Plane)
It is an imaginary flat surface bounded in front by lower border of symphysis, laterally by tip of ischial spines and posteriorly by the lower border of the last sacral vertebra (Fig. 1.1.4B).8
Figs 1.1.4A and B: The female pelvis—anatomical and Obstetrical outlet (PS—Pubic symphysis, IT—Ischial tuberosity, LSV—Last sacral vertebra, IS—Ischial spine)
The interspinous diameter is 10 cm and somewhat more. It is usually the smallest diameter of pelvis.
Anteroposterior diameter through level of ischial spine normally measures at least 11.5 cm. Its posterior sagittal diameter between the sacrum and line created by interspinous diameter is usually at least 4.5 cm.
For practical obstetrics plane of least pelvic dimension or narrow pelvic plane is the most useful landmark because of following reasons:
- It is site of origin of levator ani muscle, i.e. pelvic diaphragm.
- Ischial spines are easily felt on vaginal examination so this is important landmark for clinical documentation of descent of head, above or below the ischial spine.
- At this level pelvic axis start beginning of forward curve.
- At this level internal rotation of head takes place due to forward and downward direction of levator ani in normal labor.
Planes of Pelvis
Plane of pelvic brim, cavity and outlet are imaginary flat surface bounded by limit of pelvic brim, mid cavity and outlet.
Inclination of Pelvic Brim
Pelvis has oblique articulation with femur bones, so plane of pelvic brim in erect posture is not an horizontal surface, but is inclined at an acute angle of 55° to the horizontal surface. This is called inclination of pelvic brim.
Obstetrical Significance of Inclination of Pelvic Brim
Because of inclination of pelvic brim the posterior border of brim stands at higher level than the anterior. The sacral 10promontory is 9.4 cm above the upper border of pubic symphysis in erect position (Fig. 1.1.5A).
This fact is to be used in maneuver of breech delivery and shoulder dystocia, where posterior limb and shoulder respectively is brought anteriorly and then delivered. Diameter of bony pelvis are summarized in Table 1.1.1.
- Sub Pubic Angle = 80° ± 5°
- These diameters are reduced by soft structure lining the pelvic walls and viscera. For example, iliopsoas and obturator internus muscles reducing the transverse and oblique diameter of brim, pelvic colon in left oblique diameter of brim and cavity, urethra diminish anteroposterior diameter of outlet.
Axis of Pelvis
Axis of pelvic brim is represented by an imaginary straight line drawn perpendicular to the plane of brim at its center. If it is extended upward, it will reach umbilicus and if extended downward, it reaches upto coccyx (Fig. 1.1.5A).11
Obstetric significance: of axis of pelvic brim is that it indicates the direction of fetal descent through pelvis.
Axis of mid plane: It is represented by a line, the direction of which is intermediate between those of pelvic brim and outlet.
Axis of outlet: Axis of pelvic outlet will be represented by a line joining the center of plane of pelvic outlet with sacral promontory. At this plane axis is nearly vertical.
Anatomical Axis of Pelvis (Curve of Carus)
If we unite the axes of planes of brim, mid cavity and outlet, it frames the anatomical axis of pelvis, which travels through the center of canal of bony pelvis (Fig. 1.1.5B).
Direction of this axis is first downward and backward and then become gradually more and more forward until it reaches the axis of outlet, where it has concavity anteriorly.
Obstetrical Axis of Pelvis
Fetus passing through the pelvis does not follow the anatomical axis because pelvic cavity is almost cylindrical in upper three fourth parts. So head descends in axis of pelvic inlet till level of ischial spine and then curve forward near the plane of pelvic outlet. This represents obstetrical pelvic axis, through which head passes through pelvis.
It is a line, which is straight in upper and curved only in its lower portion (Figs 1.1.5A and B)
Pelvic Shapes
Coldwell and Moloy (1933, 1934)1,2 used special methods of stereo radiography which enabled them to study the architecture of pelvis in life size accurately. The Coldwell Moloy classification of female pelvis is still considered the gold standard for obstetrics and anticipating various obstetrical difficulties and complications in different type of pelvis.12
Figs 1.1.5A and B: The female pelvis—inclination and axis (A): AB—Horizontal line, CD—Axis of brim, EF—Plane of obstetrical outlet, GH—Axis of obstetrical outlet, (B): Obstetrical axis
Coldwell and Moloy classification is based on measurement of the greatest transverse diameter of the inlet and its division into anterior and posterior segment.
These are:
- Gynecoid
- Anthropoid
- Android
- Platypelloid
Character of posterior segment determines the type of pelvis while the character of anterior segment determines the tendency (Fig. 1.1.6)13
It is very significant to understand that type of pelvis and tendency both are determined because many pelvis are not pure, but mixed type for, e.g. Gynecoid pelvis with an android tendency means that the posterior pelvis is gynecoid and anterior pelvis is android in shape. Table 1.1.2 summarize the characteristics of four types of pelvis.
Clinical Estimation of Pelvic Size
Clinical assessment of pelvis includes a systematic palpatory assessment of pelvic inlet, cavity and outlet.
For all practical purpose clinical pelvimetry is basic for assessing pelvis and anticipating need for trial of labor, instrumental or operative delivery.
But it is an examination which calls for extreme gentle patient handling, gathering of complete information in one single examination and interpretation of clinical finding. It requires knowledge, skill and experience on part of obstetrician.
Though it is a comprehensive sensory evaluation of maternal pelvis in relation to fetal head, yet it is better to keep a specific sequence in mind. It is as follows:
- After 32 weeks, or preferably after 36 weeks of gestation, optimum conditions are found on pelvic examination. Through our experience, we strongly recommend that irrespective of finding of pelvic evaluation at 32 to 36 weeks, at onset of labor, pelvic evaluation should be reviewed. Because with force of uterine contraction and relaxation of pelvic ligaments in labor, the antenatal findings may change dramatically.
- Examination should always be done with all aseptic precautions.
- Estimation of diagonal conjugate:
- It is clinically estimated by measuring the distance from sacral promontory to lower margin of pubic symphysis. For this two fingers of dominant hand are introduced in to the vagina.
- The mobility of coccyx is evaluated.
- The anterior surface of the sacrum is next palpated from below upward and vertical and lateral curvature noted. In normal pelvis only the last three sacral vertebrae can be felt without indenting the perineum. Conversely in contracted pelvis, the entire anterior surface of sacrum is readily palpable.
- In order to reach sacral promontory, the examiner's elbow must be flexed and perineum forcibly indented by the knuckles of 3rd and 4th fingers. Index and 2nd finger are carried up and over anterior surface of sacrum. By deeply inserting the wrist, the sacral promontory may be felt by tip of second finger as a projecting bony margin.
- With fingers closely applied to the most prominent portion of sacrum, now vaginal hand is elevated until it contacts the pubic arch and this point is marked and distance between the mark and tip of second finger is the diagonal conjugate. If it is greater than 11.5 cm. It is assumed reasonably that pelvic brim is adequate for normal size fetus.15
- Obstetrical conjugate or true conjugate is calculated by subtracting 1.5 to 2.0 cm depending on height and inclination of pubic symphysis (Fig. 1.1.7).
Estimation of Mid Pelvis
Clinical estimation of mid pelvic capacity by any direct form of measurement is not possible. If ischial spines are prominent, concavity of sacrum is shallow then suspicion of a contracted pelvis should be made.
The finger in the vagina can next be swept round the lateral bays of the pelvis and with experience the ease or difficulty, with which the iliopectineal lines and side walls of the pelvis can be felt, gives idea of size of pelvis.16
Length of sacrospinous ligament is assessed. Unduly short sacrospinous ligament denotes android pelvis.
Direction of side wall of pelvis whether they are convergent, parallel or divergent gives the idea of type of pelvis (Table 1.1.2).
Estimation of Pelvis Outlet
While withdrawing the hand, transverse diameter of obstetrical outlet of the pelvis can be inferred by inserting the finger knuckles of the right hand (or closed fist) between ischial tuberosities. When knuckles of four fingers can be fitted comfortably between two ischial tuberosities, anatomical outlet is considered normal for practical purposes. After a little experience this diameter can be assessed average, small or large. Measurement of more than 8 cm can be considered normal.
At the same time shape of subpubic arch should be assessed by palpating the pubic rami from subpubic region towards the ischial tuberosities.
ASSESSMENT OF CEPHALIC PELVIC DISPROPORTION
Value of observation of clinical pelvimetry is significant only in relation to size of fetal head. So it is a gold standard saying that best pelvimeter is the fetal head.
Following observation should be integral part of clinical pelvic evaluation:
Engagement of Head
Descent of biparietal plane of the fetal head to a level below that of pelvic inlet is termed engagement. With engagement, the fetal head serves as an internal pelvimeter to demonstrate that pelvic inlet is ample for that fetus.17
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- Intermediate form are more common that pure parent type
It can be done by:
- Abdominal method
- Vaginal method
- Abdominal vaginal method
Abdominal Examination
It is less satisfactory method but in experienced hands gives quite satisfactory information. In engaged head, examining fingers can not reach the lower most part of the head. So if head is pushed downward over lower abdomen, the examining finger will slide over that position of head proximal to the biparietal plane and diverge. On the contrary in unengaged head, examining finger will converge, and easily palpate the lower part of head.
Fixed head is not necessarily engaged head. It simply shows that descent has occurred to the extent that prevents its free movement.
Vaginal Method
While doing clinical evaluation of pelvis, the situation of lowermost part of fetal head in relation to ischial spine is determined.
If lowest part of caput is at or below level of ischial spine, the head usually is engaged. In presence of caput succedaneum or considerable moulding accurate determination of engagement may be difficult.
Abdominal Vaginal Method—Muller Kerr Method
When fingers are pressed in position to measure diagonal conjugate, assistant presses upon the fundus of uterus to push the fetal head into pelvis.20
- If head can be pushed down to level of ischial spines, brim disproportion can be excluded.
- If head can not be pushed down, than thumb at pubic symphysis notes the degree of overlap. In 1st degree overlap that is 0.6 cm, parietal bone lies flush with anterior surface of pubic symphysis and these patients can deliver vaginally in presence of good uterine contraction. However if head is felt by thumb to overhang the pubic symphysis, 2nd degree overlap is diagnosed, in which possibility of safe vaginal delivery is quite less (Fig. 1.1.8).
MATERNAL SOFT TISSUES
Beside bony pelvis of mother, maternal soft tissue—its anatomy as well variation in thickness, texture, and 21disposition plays an important role in vaginal delivery. Beside this all obstetric operations and maneuvers are done in relation to maternal soft tissues. So it is necessary to have a clear concept of not only the anatomy of pelvic floor and perieneum but also its dynamic changes which occur in process of child birth.
PELVIC FLOOR
Pelvic floor comprise the soft parts which fill in pelvic outlet. For obstetrical purpose the most important structure of pelvic floor are:
- Pelvic fascia
- Levator ani muscle and coccygeus muscle (pelvic diaphragm)
- Urogenital diaphragm
Pelvic Fascia
Pelvic facia is visceral layer which springs from the fascia clothing the lateral pelvic wall at level of white line which corresponds to level of ischial spine. This fascia is split into superior and inferior layer to enclose the muscle.
Levator Ani and Coccygeues Muscle (Pelvic Diaphragm)
Levator ani muscle slings that originates from the posterior surface of the superior pubic rami, inner surface of ischial spine and obturator fascia.
This muscle and fascia together form a pelvic diaphragm closing in the pelvic cavity and some of these muscle fibers are inserted around the vagina and rectum to form an efficient functional sphincter. The rectum actually pierces the common central linear tendon of insertion of the two Levator Ani muscle. In a recent study 22utilizing MRI3,4 reported significant variation in levator ani muscle and endopelvic fascia and urethral support in nulliparous women (Fig. 1.1.9).
Urogenital Diaphragm
The urogenital diaphragm is external to pelvic diaphragm.
It is made up of:
- Deep transverse perineal muscle
- Constrictor of urethra
- Internal and external fascial covering
It is pierced by urethra between inner borders of pubo-rectalis portion of levator ani muscles.
Blood Supply of Pelvic Floor and Perineum is via internal pudendal artery and its branches that is—inferior rectal artery and posterior labial artery.
Innervation of perineum is primarily via the pudendal nerve and its branches which originate from S2, S3 and S4 level of spinal cord.
Perineal Body
The median raphe of levator ani between the anus and vagina is reinforced by the central tendon of the perineum. The bulbocavernous, superficial transverse perineal and external anal sphincter muscle also converge on central tendon. The center of perineal body is 3 cm below the level of a line joining the lower border of symphysis with tip of coccyx.
All these structure contribute to perineal body, which provides support for perineum (Fig. 1.1.9).
OBSTETRIC DYNAMICS OF PELVIC FLOOR
During vaginal delivery and especially in 2nd stage of labor the vagina that is in center of pelvic floor become enormously dilated and in result the disposition of pelvic floor is changed.23
The dilated vagina divides the pelvic floor into two parts:
- Anterior section in front of vagina, which is drawn upward and forward and
- Posterior section lying behind vagina which is displaced downwards and backwards.
Fetus is expelled through space between anterior and posterior section like—Swing doors by pulling one door towards you and pushing the other way.
Because of upward displacement of anterior section in 2nd stage of labor, the bladder which was initially a pelvic organ lying behind symphysis pubis, now drawn up above the pubic symphysis into the abdomen and urethra is considerably elongated.
In posterior section in 2nd stage of labor the fourchette is greatly thinned and perineal body is stretched and become convex and lengthened from anus to vulva (Fig. 1.1.10).24
So the fourchettle becomes the lowest part of the pelvic floor—10 cm below the coccyges symphysial level, the projection of this portion of pelvic floor is thus increased to 10 cm and wide aperture of exit is provided for the fetus.
The combination of displacement of anterior and posterior section prolong the pelvic canal by formation of a tube composed solely of soft parts below level of pelvic outlet. Very interestingly this tube of soft part has the shallow anterior wall but deep posterior and lateral wall like cavity of true bony pelvis.25
So axis of prolongation of soft part forms in continuation of axis of bony pelvis.
This great dilatation of vaginal canal and elongation of posterior wall during birth of child essentially inflicts certain injury upon the muscles fibers and when there is severe injury it may cause permanent weakness of pelvic floor which can result in prolapse of vaginal wall, bladder or even uterine ligaments.
CONCLUDING REMARK
Understanding the basics of anatomical variation of pelvis and its effect on course of vaginal delivery is foundation of obstetrics. Clinical observation starts right in antenatal period with body mass index estimation, and body shapes variation and continues till delivery of the baby. Correct method of examination of pelvis and clinical diagnosis of fetopelvic proportion or disproportion is one of the basic and important obstetric skill which is to be learnt throughout the obstetric career. Two knowledgeable and sensitive fingers of obstetrician can outweigh the radiological and even MRI examination.
REFERENCES
- Caldwell WE, Moloy HC. Anatomical variation in the female pelvis and their effects in labor with a suggested classification; Am J Obstet Gynecol 1933;26:479.
- Caldwell WE, Moloy HC, D' Esopo DA. Further studies on the pelvic architecture. Am J Obstet Gynecol 1934;28:482.
- Tunn R, Delancey JO, Howard D, et al. Anatomical Variations in the levator ani muscle, endopelvic fascia and urethra in nulliperus evaluated by magnetic resonance imaging. Am J Obstet Gynecol 2003;188:116.
- Hoyte L, Jababm, Warfield SK, et al. Levator Ani Thickness variation in symptomatic and asymptomatic women using magnetic resonance based 3 diamensional color mapping. Am J Obstet Gynecol 2004;191:856.
The journey of fetus from maternal passage to outer world is considered most dangerous and difficult one of the human life.
Dimensions, disposition and specific characteristics of fetus in relation to maternal passage is critical to route of delivery. So let's review the facts and diagnosis of fetal positions in laboring women.
Fetal Lie
It denotes the relation of long axis of fetus to that of uterine ovoid. It may be longitudinal or transverse or occasionally oblique at 45° angle which is considered unstable and always becomes longitudinal or transverse in course of labor.
Longitudinal lie are present in over 99% of labor at term. When long axis of fetal and uterine ovoid correspond, lie is said to be longitudinal. It may be both head (97%) or breech below (2.5%).1 Transverse or oblique lie is said when long axis of fetus and uterine ovoid do not correspond (0.5%).
Fetal Presentation
Part of fetus which lies below and presents at pelvic brim is called fetal presentation which may be (a) cephalic (b) breech, (c) shoulder.
Presenting Part of Fetus
It is more precisely the particular part of fetal presentation, which first enters the pelvic brim and like wise first to be felt by examining finger during pelvic examinations. In majority of cephalic presentation it is vertex presentation.27
Disposition of Fetus—Fetal Attitude or Posture
During last weeks of pregnancy the head, trunk and limb of fetus are packed up into smallest possible space in a regular and fairly constant arrangement of generalized flexion—this is termed as fetal attitude.
Fetus become folded or bent upon itself in such a manner that back becomes convex, chin is almost in contact with chest, thighs are flexed over abdomen, legs are bent at knees and the arches of feet rest upon the anterior surfaces of the legs, arms are closed over thorax and umbilical cord lies in the space between them and lower extremities (Fig. 1.2.1).
This characteristic fetal posture results from mode of growth of fetus and its accommodation to uterine cavity. If fetal head become extended from vertex to face presentation, it results in progressive change in fetal attitude from a convex (flexed) to a concave (extended) contour of the vertebral column.
Fetal Skull
From obstetrical point of view the characteristic of fetal skull and size of fetal head is important because firstly head is presenting part in more than 90% of labor and secondly an essential feature of labor is the adaptation between the fetal head and maternal bony pelvis.
Ossification of the fetal skull at term pregnancy is incomplete, especially of the vault bones. So bones of base of fetal skull are firm and incompressible, while the tabular bones of vault remain thin and pliable.
These pliable vault bones are separated at their edges by interval of unossified membranes, which form the sutures and fontanelles.
Sutures
- Sagittal suture: It cross the vault of skull in middle line, in an anteroposterior direction between two parietal bones (Fig. 1.2.2—a).
- Frontal suture: Sagittal suture continues in front beyond the anterior fontanelle, in the same plane between two halves of frontal bones (Fig. 1.2.2—f).
- Coronal suture: It separates the frontal from parietal bones meeting the sagittal and frontal suture at the anterior frontanelle (Fig. 1.2.2—d).
- Lambdoidal suture: It separates the parietal bone from the tabular portion of the occipital bone (Fig. 1.2.2— b).29
Fontanelles
Where several sutures meet, an irregular space forms, which is enclosed by a membrane and designated as fontanelle. Six fontanelles exist on the fetal skull at term, but only two—anterior and posterior fontanelles are of practical importance.
Anterior Fontanelle (Bregma)
It is an unequal sided kite shaped piece of unossified membrane, lying in mesial plane between two halves of frontal and two parietal bones. Its angle are continuous with frontal, sagittal and right and left halves of the coronal suture. It measures 3 cm in anteroposterior and 2 cm in transverse diameter. As it lies a little below the general level of the skull, it can felt on the surface as a shallow depression (Fig. 1.2.2—e).
Posterior Fontanelle
It is a small triangular depressed area at the intersection of the sagittal and lambdoid suture. It is to be noted that it is not an unossified piece of membrane at all but depression, except in a premature fetus (Fig. 1.2.2—c).
Temporal or cesarean fontanelle have no diagnostic significance.
Obstetrical Significance of Anterior and Posterior Fontanelle
These two fontanelles are of great clinical obstetrical significance because they can be recognized during labor via its special characteristics and from them valuable information can be obtained regarding position and attitude of the fetal head.
Fig. 1.2.2: Fetal vault—suture fontanelles (a—sagittal suture, b—lambdoidal suture, c—posterior fontanelle, d—coronal suture, e—anterior fontanelle, f—frontal suture)
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Diameters and Circumference of Fetal Head
General shape of the fetal head is that of an ovoid with a long anteroposterior diameter. In a normal attitude of complete flexion, long diameter of fetal head ovoid forms a very acute angle with that of body ovoid (Figs 1.2.3A to D).31
If head lies mid way between flexion and extension, the two long diameter cross each other at right angles. And if head is fully extended the angle formed is obtuse and the face becomes the lowest part.
This relationship of head with body is basis of different diameter of engagement in cephalic presentations.
Girdle of contact is that part of circumference of head which first comes in contact with pelvic brim. Diameter of girdle of contact is called diameter of engagement.
Vertex is area of vault of skull which is bounded in front by anterior fontanelle and coronal suture behind by posterior fontanelle and lambdoid suture and laterally by lines passing through parietal eminences.
It is most common and favoured cephalic presentation occurs in fully flexed head presenting subocciputo bregmatic diameter for engagement which is shortest diameter of fetal skull.
Figs 1.2.3A to D: Different diameters of engagement with varying attitudes of fetal head: (A) Completely flexed vertex: engagement of sub-occipito-bregmatic diameter, (B) Extended vertex: engagement of occipito-frontal-diameter, (C) Brow presentation: engagement of mento vertical diameter, (D) Completely extended face: engagement of sub-mento-bregmatic diameter
Different diameters of engagement with different cephalic presentation are illustrated in Table 1.2.2.
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Transverse Diameter of Fetal Skull
- Biparietal diameter—9.4 cm, between two parietal eminence
- Bitemporal diameter—8.1 cm, between anteroinferior ends of coronal suture
- Bimastoid—7.5 cm, between tip of mastoid process.
Facts of Obstetrical Significance
- Greatest circumference of head, corresponds to plane of occipito frontal diameter, average 34.5 cm, is too large to fit through pelvis without flexion.
- Smallest circumference correspond to plane of suboccipito bregmatic diameter is 32 cm.
- As vault is compressible, all diameter can be reduced in length to an appreciable extent during passage of head through pelvis.
- Moulding—As the bones of the cranium are normally connected only by a thin layer of fibrous tissue that allows considerable shifting or sliding of each bone to accommodate size and shape of maternal pelvis. This intrapartum process is termed moulding. It can result in reduction of all diameters.
Fetal Position and Denominator
Fetal denominator is a bony point on fetal presenting part in relation to designated location of maternal pelvis. Position refers to the relationship of denominator to right or left side of maternal birth canal. Fetal occiput, chin (mentum) and sacrum are the determining point in vertex, face and breech presentation respectively.
So with each presentation, there may be two positions—right or left. So there are right or left occupital, right left mentum and right and left sacral presentation.34
Varieties of Presentation and Positions
For still more accurate orientation, the relationship of a given position of the presenting part to the anterior, transverse or posterior part of maternal pelvis is considered.
As the presenting part in right or left positions may be directed Anteriorly (A), Transversely (T) or Posteriorly (P), there are six variables of each of three presentations.
Thus in occiput presentation the presentation, position and variety may be abbreviated in clockwise fashion.
- 1st position—LOA
- 2nd position—ROA
- 3rd position—ROP
- 4th position—LOP
In majority of cases the vertex enters the pelvis with sagittal suture lying in transverse pelvic diameter. The fetus enters into pelvis in left occiput transverse (LOT) positions in 40% of labor and in right occiput transverse (ROT) position in 20%. In occiput anterior position (LOA or ROA), the head either enters the pelvis with occiput rotated 45%, anteriorly from the transverse position or subsequently does so. In 20% of labor the fetus enters the pelvis in an occiput posterior (OP) positions1 (Figs 1.2.4A and B).
While the mechanism of labor in transverse and anterior position are usually similar, posterior position are more often associated with narrow forepelvis.
- Vertex engage in right oblique diameter much oftener than left because left oblique diameter is enroached upon by pelvic colon and rectum.
Figs 1.2.4A and B: Variants of positions of fetus: (A) Occiput anterior position, (B) Occiput posterior position
Asynclitism (Parietal Obliquity)
When vertex is engaged in pelvic brim, owing to lateral inclination of head, one parietal bone usually lies at a lower level than other, so the sagittal suture does not correspond precisely to either the transverse or oblique diameter, but lies either in front or behind it.
- Anterior asynclitism: If sagittal suture approaches the sacral promontory, anterior parietal bone is below the posterior and presents itself to the examining finger. It is called Anterior Asynclitism, or anterior parietal obliquity or Naegele's obliquity. It is found chiefly in multipara (see Fig. 1.3.2A).
- Posterior asynclitism: If sagittal suture lies close to symphysis, posterior parietal bone will be below the anterior and present to examining finger. It is called Posterior Asynclitism, posterior parietal obliquity or Litzman's obliquity (see Fig. 1.3.2B). It is found chiefly in primigravida because in primigravida the relatively tense abdominal wall tends to keep the uterus back and so prevent body of fetus from coming forward into line of axis of the brim.
Moderate degrees of asynclitism are rule in normal labor. But severe and persistent asynclitism is abnormal and only occurs with varieties of contracted pelvis.
CONCLUDING REMARK
En route to vaginal delivery through maternal passage, obstetrician is most concerned for the safety of passenger that is fetus, which is going to be delivered.
Understanding the special anatomical characteristics of fetus and clinical interpretation of different landmark of fetal parts in relation to maternal pelvis is another foundation stone of obstetrics.
REFERENCES
- Gardberg M, Tuppurnainen M. Anterior placenta location predisposes for occipito posterior presentation near term. Acta Obstet Gynecol Scand 1994a;73:151.
The positional change in the presenting part required to navigate the pelvic canal constitute the mechanism of labor.
These series of movement of fetus alter its relationship to the pelvic canal. Customarily these movements are described as movement of head, but virtually head is only the index of movement, trunk also initiates and participates in some movements.
CARDINAL MOVEMENT OF LABOR
- Engagement
- Descent
- Flexion
- Internal rotation
- Extension
- External rotation
- Expulsion
It should be understood that these movement are sequential as well overlap, e.g. descent is more or less continuous movement and in engagement, there is both flexion as well descent of head (Figs 1.3.1A to H).
Beside this concomitant uterine contraction modify fetal attitude. These modification causes straightening of fetus, with loss of dorsal convexity and closer application of extremities to the body so fetal ovoid is transformed into a cylinder, with smallest possible cross-section typically passing through birth canal.
Figs 1.3.1A to H: Cardinal movement of labor: (A) Engagement, (B, C) Descent flexion, (D) Internal rotation, (E, F) Head delivered by extension, (G, H) Delivery of anterior and posterior shoulder
Engagement
The mechanism by which the biparietal diameter, that is the greatest transverse diameter of fetal head in occiput presentation, passes through the pelvic inlet is designated ‘Engagement’.
- Timing of engagement: The fetal head may engage during the last few weeks of pregnancy or not until after onset of labor. In many multipara and even in few nulliparous women, the fetal head is freely movable above the pelvic inlet at the onset of labor. It is sometimes referred as floating head.But it is to be emphasized that with finding of floating head even in nullipara, fetal position and pelvic assessment should be reviewed during course of active labor.
- With engagement anterior or posterior asynclitism occur which is a lateral deflection of head to a more anterior or posterior position in the pelvis. Successive shifting from posterior to anterior asynclitism helps in descent (Figs 1.3.2A and B).
Descent
Throughout first and second stage of labor there is more or less continuous movement of descent. Descent of fetus is first requisite for birth of newborn. Descent is brought about by following forces:
- Pressure of the amniotic fluid.
- Direct pressure of the fundus upon the breech with contraction.
- Bearing down effort of maternal abdominal muscle.
In nulliprara engagement may occur before onset of labor, and further descent may not follow until beginning of 2nd stage of labor, in multiparous women, descent usually starts with movement of engagement.41
Flexion
Flexion is primarily an attitude of fetus but usually at onset of labor head enter the pelvic brim in an attitude of deficient flexion.
With start of labor, flexion is increased because of following facts:
- With descent of head when at start of labor, the head begins to meet resistance during its passage through the birth canal, flexion is increased. It occurs because fetal head represents a two armed lever, with fulcrum at occipito Atlantoid joint. And whose anterior arm is longer than the posterior. So when fetal head meets resistance, long-arm of lever ascends and short arm descends, thus brings occiput lower than forehead and increasing flexion (Figs 1.3.1B and C). Strong uterine contraction encourages flexion.
- Point of flexion Point at which movement of increased flexion occurs, varies. Normally it occurs at level of pelvic floor, but when there is disproportion between head and pelvis especially in generalized contracted pelvis, extreme flexion can occur at pelvic brim.
- Significance of flexion Complete flexion of head poses great mechanical advantage in vaginal delivery in vertex presentation, because in this position the plane of engagement is suboccipito bregmatic, which is not only smallest possible, but also has the shape which easily pass through maternal pelvic canal. In less flexed head suboccipito frontal diameter engages which is bigger and its plane is approximately quadrilateral, so not well adapted to pass through the pelvis. When head is mid way between complete flexion and complete extension in vertex presentation, the occipito frontal diameter is engaged which also has quadri-lateral shape and bigger in size (Fig. 1.2.3B).42
Internal Rotation
This movement consist of turning of the head in such a manner that the occiput gradually moves toward the symphysis pubis anteriorly from its original position or less commonly posteriorly towards the shallow of sacrum. It is essential step for completion of labor unless fetus is unusually small.
Mechanism of Internal Rotation
The tendency of head for forward or internal rotation of occiput is caused by following anatomic and dynamic factors:
- Sloping character of pelvic floor caused by downward and forward direction of Levator Ani muscle. Levator ani muscle and soft part of pelvic floor form a curved plane or gutter which is directed downward, forward and inward towards mid line.
- Unequal flexibility of different part of fetus.
- If there is any movable body or fetus head which reaches pelvis floor and driven by force above caused by uterine contraction, fetus moves in the direction of pelvic floor. In flexed head occiput reach in advance of sinciput, so occiput rotates under the pubic arch. This internal rotation occurs in occiput anterior transverse or posterior position. As pelvic floor is difficient anteriorly head easily moves forward in direction of least resistance. When occiput is posterior at level of pelvic floor, the longer is this arc of rotation and in oblique posterior position it amounts to 3/8th of circle or 135°. Mechanically it aids the movement of internal rotation (Figs 1.3.3A and B).
Extension
Now head is delivered by movement of extension. When head presses upon pelvic floor, two force acts:43
Figs 1.3.3A and B: Anterior rotation from ROA and ROP position (A) 1/4th of circle, (B) 3/8th of circle
Mechanism of Extension
- Uterine forces acting more posteriorly
- Force of resistant pelvic floor and symphysis acting more anteriorly. The resultant vector is in direction of vulvar opening, thereby causing extension of head, which brings the base of occiput into direct contact with inferior margins of symphysis pubis.
Sequence of Movement of Extension
With progressive distension of perineum and vaginal opening, an increasingly large portion of occiput gradually appears and head is born in following sequence with movement of extension (Figs 1.3.4):
Occiput →Bregma → Forehead → Nose → Mouth—finally chin passes successively over anterior margin of perineum (see Figs 1.3.1E and F).
Immediately after delivery of head, the head drops downward so that the chin lies over maternal anal region. It is to be observed that interval between chin and chest wall progressively increases as head is expelled and back of neck become bent round the pubis.44
Restitution and External Rotation
These two movements are movement of neck and trunk and head at this junction is merely the index.
Restitution
when head emerges in anteroposterior diameter of outlet, the shoulder engage in oblique diameter of brim, so there is slight twist of neck. When head is delivered there is a slight movement, so neck is back into normal relation to the bisacromial diameter.
If occiput was originally directed toward left, head rotate toward left ischial tuberosity, if occiput was originally directed toward right, occiput rotate to the right. This is a passive movement by which head returns to realign itself with shoulders.45
External Rotation
It is movement of shoulder from oblique diameter of brim to anteroposterior diameter of outlet, and now shoulders are delivered. It can also be called as the internal rotation of the shoulder. This is reflected externally as a passive movement of head which is rotated further in same direction as restitution. So along with restitution, movement of external rotation bring bisacromial diameter into relation with anteroposterior diameter of the pelvic outlet (see Figs 1.3.1G and H).
Thus one shoulder is anterior behind the pubic symphysis and other is posterior. Mechanical pelvic factors causing internal rotation also causes external rotation. In these movements, occiput always moves to the side, where it lay at the beginning of labor.
Expulsion
Immediately after external rotation, the anterior shoulder appears under symphysis pubis and perineum becomes distended by posterior shoulder.
After delivery of shoulder, rest of body is delivered quickly.
CONCLUDING REMARK
Series of movement of fetus during journey through maternal passage depicts a beautiful harmony created by anatomical and physiological facts and variation of fetal presenting part as well maternal pelvis. Clear understanding of the movement of fetus is one of the basic knowledge which helps obstetrician in conducting vaginal delivery and diagnosing dysfunctional labor.46
1.4. STAGES OF LABOR
“Labor” is the process by which a fetus of viable age is expelled from the uterus. It varies greatly in duration, severity, and risk involved to mother and fetus.
New Shorter Oxford English dictionary says meaning of Labor - Toil, Trouble, Suffering, Bodily painful exertion and outcome of work, strangely all meaning is implicated appropriate for the process of child birth and emphasize the need of supportive care for laboring women.
The WHO defines Normal labor as one in which fetus presents by the vertex, begins spontaneously in at term and terminates naturally without artificial aid and without complications.
Abnormal labor is somewhat difficult to define, but for practical purpose it may include all cases in which some part other than the vertex presents and all vertex cases in which maternal or fetal complications arise.
The role of obstetric caregiver should be based on evidence based practice; modified/obstetric skill and women's personal preferences. One should avoid unnecessary intervention in course of normal labor, but at the same time identify and intervene, when things start going amiss.
Within class of normal labor many condition should be recognized that may effect the degree of difficulty to be encountered in process of labor.
Generally speaking, primigravidae and extremes of age poses longer duration and difficulty during childbirth.
CALCULATION OF DATE OF LABOR
One of most frequently asked question by women is the date of delivery. The date at which labor may be expected cannot be predicted with certainty.47
The real duration of pregnancy is from the moment of fertilization of women until the occurrence of labor and birth of the child.
This is known as fertilization—labor interval and it cannot be calculated because there is no method of knowing exact time of fertilization.
All our knowledge about duration of pregnancy is derived from statistical data that take as the new point either the first day of last menstrual period or date of single coitus (menstrual labor and insemination labor interval respectively).
All the statistical studies have only confirmed the belief held throughout the ages that in average women labor may be expected about 280 days or ten lunar months following the first day of the last menstruation, although children of apparently normal maturity may be born as many as 20 or more days short of or in excess of the average duration.
A calculation of date of labor based on the date of last menstrual period is still the common and most accurate method we possess. Calculation is made by adding 7 days to the date of last menstrual period and counting forward 9 calendar months or counting back 3 months.
When the date of last menstrual period is not known or women conceive in lactational amenorrhea, clinical criteria of calculation is height of uterus above pubis. Ultrasonic dating nowadays plays important role in calculation of the date of labor especially ultrasound examination performed in early pregnancy.
CAUSE OF ONSET OF LABOR
This physiological process that regulate parturition and onset of labor continue to be defined. Onset of labor represents the culmination of series of biochemical changes 48in uterus that result from endocrine and paracrine signals coming from both the mother and the fetus. Some of the factor that are closely involved are:
- Uterus sensitivity to chemicohormonal influence and stretch
- Fetal anterior pituitary adrenal system
- Placenta estrogen and progestagen formation
- Maternal estrogen, progestogen, oxytocin and prostaglandins production.
Presently we can explain onset of labor after and ongoing clinical and para-clinical research work that increasing fetal anterior pituitary adrenal activity brings about increasing production of estrogen and of surfactant.
Surfactant causes lung maturation while estrogen combined with oxytocin is responsible for release of prostaglandin from decidual and myometrial cells. This release is delayed until level of progesterone falls to a figure which is now no longer effective in its inhibitory action.
PHASES OF PARTURITION
Parturition: Bringing forth of young includes all physiological process involved in birthing. It can be divided into four uterine phase (Table 1.4.1), which corresponds to major physiological transition of myometrium and cervix during pregnancy.
|
Phase Zero—Parturition
Characterized by uterine smooth muscle quiescence with maintenance of structural integrity.
Myometrium tranquility of phase 0 is continued till near the end of pregnancy.
Phase One of Parturition—Preparation for Labor
Near end of pregnancy, Myometrium is awakened or activated. This phase represents the sequence of change of uterus during last 6 to 8 weeks of pregnancy.
In this phase there is alteration in expression of key protein that control myometrial contractility which are termed CAPs (Contraction Associated Protein) and there is striking increase in myometrial oxytocin receptors which result in increased uterine contractile and responsiveness to uterotonics.
At the same time, cervix responds quiet differently and with initiation of parturition the cervix softens, yield and becomes more readily dilatable.
These cervical modifications involve change in connective tissues associated with invasion by inflammatory cells. In late pregnancy there is increase in collagen breakdown and rearrangement of collagen fibers bundles and striking increase in amount of hyaluronic acid in the cervix with concomitant increase in water and decrease in dermaton sulfate needed for collagen fiber cross linking.
Simultaneous increase of uterine contractility and dilatability of cervix causes formation of lower uterine segment in phase I.
In which fetal head often descends to or even through the pelvic inlet—which is referred as Lightening.
It may be possible that the Myometrium in lower segment is unique from adjacent myometrium in upper 50uterine segment which have distinct role during labor (Further detail in Unit 3.1).
Sign that Precede Labor—Phase I
Women often describe feeling different, restless, odd prior to going into labor. Women experience a shift in their priorities as the birth becomes imminent, evidenced by spurts of energy and nesting activities.
For days and even weeks, before labor, many women experience separated contractions that eventually disappear. They may experience lower backache and deep pelvic discomfort as the baby descends in the pelvis.1
Phase II of Parturition: The Process of Labor
It is synonymous with active labor. That is uterine contraction that brings about progressive cervical dilatation and delivery.
It is customarily divided into three stages:
- Ist stage of labor: Stage of cervical effacement and dilatation.
- IInd stage of labor: It begins with full dilatation of cervix and ends with delivery of fetus—so it is a stage of expulsion of fetus.
- IIIrd stage of labor: It begins immediately after delivery of fetus and ends with delivery of placenta and fetal membranes—so it is a stage of separation and expulsion of placenta.
ONSET OF LABOR
To recognize onset of labor is one of the most difficult part of management of labor. The strict definition of labor— uterine contractions that bring about recognizable effacement and dilatation of cervix—usually does not 51easily help the clinician in determination of time of start of labor because this can only be confirmed retrospectively.
However, the signs on which start of labor is diagnosed should be clearly understood. These are as follows:
- Painful uterine contraction
- Slight uterine hemorrhage—the show
- Start of dilatation of the internal Os
- Formation of the bag of water.
Painful Uterine Contraction (Labor Pain)
Intermittent contractions recognizable on palpation occur in wall of gravid uterus. But they are usually not perceived by the patient and produce no effect upon the cervix.
At term characteristics of these contraction changes. They become more regular, gradually increase in severity and become more prolonged and palpable on uterine palpation.
So called false labor pains are caused by uterine activity that causes discomfort because they reach pain threshold, but not accompanied by retraction responsible for dilatation of cervix. These uterine contractions may develop at any time during pregnancy and these false labor pains can stop spontaneously or it may proceed rapidly into effective uterine activity.
Sometime colicky abdominal pain is caused by trivial reason as dyspepsia or constipation.
Slight Uterine Hemorrhage—the Show
It is per vaginal discharge of blood stained mucus which comes from abundantly secreted cervical mucous during labor, and hemorrhage caused by separation of membrane from lower uterine segment at beginning of cervical dilatation.52
Dilatation of Internal Os
The length, dilatation as well texture of cervix before onset of labor, at term is variable. At term the ripe cervix is soft, effaced, slightly patulous and closely applied to head.
Dilatation of internal Os is accompanied by stretching of lowest part of the lower uterine segment so the cervix will be found shortened when head is deeply engaged, even when women is not in labor, not an uncommon finding especially in multigravidae (Fig. 1.4.1A).
So a closed cervix is a reliable sign that labor has not started, a slightly dilated cervix may be found in woman who is not in labor.
Formation of Bag of Water
On dilatation of cervix, the lower pole of fetal membrane that is chorion and amnion, which has been already separated few weeks before actual onset of labor by stretching of lower uterine segment, now bulge into cervical canal. This bulge of membrane containing a little liquor amni is called the presence of bag of water, which becomes tense and convex during uterine contraction and disappears with passing off the pain.
Even with full understanding of these points it is sometimes difficult to decide from a single examination that patient is actually in labor or not.
O Driscoll and Colleague (1984)2 has made an effort to codify admission criteria. There criteria are—at term painful uterine contraction accompanied by any one of the following – either ruptured membrane, bloody show or complete cervical effacement.53
FIRST STAGE OF LABOR
First stage of labor is stage of dilatation of the cervix which is preparatory to the actual process of birth or expulsion of fetus from the uterus. It's progress or non-progress can be judged clinically by changes taking place in the cervix, external Os and bag of water.
At onset of labor the vaginal portion of the cervix is distinctly felt, forming a projection of about ½” in length. As the internal Os opens, the upper part of cervical canal merges in lower uterine segment. With progressive dilatation more of the cervix taken “is up” into uterus, which can be detected clinically by per vaginal examination as a shortening of the cervical projection.
When there is no definite cervical projection, felt by finger on per vaginal examination, cervix is said to be taken up although ext Os may still be only partially dilated (Fig. 1.4.1A).
In a primigravidae the cervix always dilates from above downwards. Ext Os offers great resistance and undergoes little dilatation until the cervical canal is completely taken up.
In multigravidae ext Os is usually sufficiently open even before onset of labor, and offers less resistance to force of dilatation. So in multigravidae, taking up of the canal and dilatation of the ext Os occur and advance simultaneously and even fully dilated Os presents thick edges. With progressive dilatation of ext Os of cervix and taking up of cervix into uterus, the bag of water bulges slightly through dilating ext Os in the shape of an inverted watch glass. Bag of water usually rupture spontaneously near full dilatation of cervix, but may rupture even before onset of labor in early first stage of labor.54
Duration of first stage of labor is variable, on the average 8 to 16 hours in the primigravidae and 4 to 8 hours in multigravidae.
Above progressive changes in cervix in first stage of labor were scientifically studied by Friedman (1954)3 for assessing and predicting the progress of normal labor with use of graphical approach, based on statistical observation.
Friedman developed the concept of three functional division of labor to describe the physiological objective of each division.
- Preparatory division: In this division there is little dilatation of cervix but connective tissue component of cervix change considerably. Sedation and conduction analgesia are capable of arresting this division of labor.
- Dilatational division: In this phase cervical dilatation proceed at its most rapid rate and this is unaffected by sedation or conduction analgesia.
- Pelvic division: It starts with deceleration phase of cervical dilation. The classical mechanism of labor that include the cardinal fetal movement of the cephalic presentation—that is engagement, flexion, descent, internal rotation, extension and external rotation takes place principally during the pelvic division (Fig. 1.4.1A).
The overall pattern of cervical dilatation during preparatory and dilatation division of normal labor is sigmoid curve. The latent phase corresponds to preparatory division and active phase correspond to dilatational division. Friedman subdivided the active phase into further three phase:
- Acceleration phase
- Phase of maximum slope, and
Fig. 1.4.1A: Graphic display progress of labor with gradual dilatation of cervix in first stage of labor (a—Preparatory division, b—Dilatational division, c—Pelvic division)
Latent Phase
The onset of latent labor as defined by Friedman (1972) is the point at which mother perceives regular contraction and it ends usually between 3 to 5 cm of dilatation.
It is said to be prolonged if > 20 hours in nullipara and > 14 hours in multipara. Latent phase can be effected by various causes as well interference like epidural analgesia, excessive sedation, thick uneffaced or undilatated cervix.56
The concept of a latent phase has helped significantly in understanding normal human labor because labor is considerably longer when a latent phase is included. For women planning hospital birth, home is probably the best place to spend the latent phase and not hospital environment, where fear and anxiety are likely to inhibit labor and attract interventions.4
Women's Characteristic Behavior in Latent Phase
Women may be excited or may be anxious. They usually want confirmation of what is happening to their body as well as seeking reassurance and a rapport with attending person. Primigravidae in their excitement and inexperience of strong labor can sometimes overestimate their progress. They need their excitement and fears acknowledged.5
Active Labor
The cervical dilatation of 3 to 5 cm or more, in presence of uterine contraction can be taken to represent threshold for active labor. Cervix of active labor provide useful guidelines and guidepost for labor management. 25% of nulliparaous labor and 15% of multigravid have one or other form of active labor phase abnormalities.6
Friedman subdivided active phase problem into:
- Protraction disorder which is defined as a slow rate of cervical dilatation or descent which for nullipara was less than 1.2 cm dilatation per hour or less than 1 cm descent per hour. For multipara protraction was defined as less than 1.5 cm dilatation per hour or less than 2 cm descent per hour.
Factors contributed to both protractive and arrest disorder were excessive sedation, vaginal analgesia, fetal malposition. Cephalopelvic disproportion has to be excluded before expectant management of active phase abnormalities like oxytocin induction or Artificial Rupture Of Membrane (AROM).
There have been certain variation and difference of opinion by various workers on Friedman's curve and conclusions.
Hendricks (1970)7 stated that there is absence of latent phase, no deceleration phase, and brevity of labor in their observation. They also noted the similar rate of cervical dilatation for nulliparae and multiparae after 4 cm.
Zhang and Colleague (2002)8 observed markedly different labor curve from Friedman curve. In their study cervical rate of dilatation was slow in active phase and took 5.5 hours to progress from 4 cm to 10 cm compared with 2.5 hours in the Friedman's curve.
Alexander et al (2002)9 found that epidural analgesia lengthens the active phase of Friedman's labor curve by one hour.
Gurewitsch et al (2002, 2003)10,11 in the study of labor and descent curve of women with high and low parity concluded that poor progress from 4 to 6 cm should not be considered abnormal and the women with high parity should not be expected to progress faster than those with lower parity.
Women's Characteristic Behavior in Active Phase
In the earlier stage of labor, the woman may continue to eat and drink or laugh or talk excitably between contraction. As the labor advance the women is less inclined to eat or talk and she will become quieter and behave more instinctively as the primitive part of brain is taken over (Ockenden 2001).1258
In stronger labor, the women is more focused and withdrawn, she can be described as having “gone into herself.” As labor become stronger, the women is less mobile, holding on to something during a contraction or standing legs astride. With advancement of labor she may close her eyes and her breathing usually becomes heavier and more controlled (Burvill 2002).1 Women may moan or occasionally call out during the most painful contraction. Women can often be observed to curl their toes as the contraction peaks.
If women talks it will be brief such as water when wanting a drink, or back to instruct someone to rub her back, this is not the time to talk to her or to draw her out from herself.
So many time the attendant and doctors are not familiar with women's typical behavior in labor and they need explanation and guidance as not to disturb the women, particularly during uterine contraction.
When doctor/midwife needs to check the fetal heart sound, she should first speak in quiet voice, or simply touch the women's arm prior to that, and depending on the relationship with women, not always expect an answer.
Second Stage of Labor
This stage begins when cervical dilatation is complete and ends with fetal delivery. The presenting part is now passing from the cervix into the vagina and on examination the lip of ext Os can not be felt. In this stage the vagina is gradually dilated from above downwards by the passage through it of the head and body of fetus. In this stage uterus, cervix and vagina is merged into a single broad channel, the boundaries between component parts are obliterated.59
The expulsion of child is caused by severe uterine contraction, strongly reinforced by voluntary muscles. Vigorous use of voluntary muscles by women is the chief factor in causing the characteristic feature of the pain of the second stage.
Each uterine contraction pain is associated with deep inspiration, followed by straining or bearing down, in which patient holds her breath and employs her diaphragm, abdominal or back muscles and sometimes apparently all the muscles in her body. The face become congested, the pulse quickens, perspiration occurs and patient groans deeply during the pains. They last much longer and recur very early as compared to first stage.
Change observed in external genitals on reaching of head in the pelvic floor is:
- Stretching of perineal body, which during the pain becomes somewhat convex externally and lengthened from anus to vulva.
- Anus becomes turgid and dilates slightly and the hairy scalp appears at vulva. Initially between uterine contraction and pain, the ext genitalia resume their normal appearance (Fig. 1.4.1B).
- When head is about to emerge there is gaping of anus, exposing 1–2” of anterior rectal wall, fourchette is thinned and there may be a certain degree of laceration of post vaginal wall. At this time a small perineotomy can be given (Figs 1.4.1B).
- The actual expulsion of fetal head is accompanied by a very prolonged and severe contraction, or series of powerful contraction, accompanied by violent straining.
- After delivery of head there is short pause, immediately to be followed by return of pain in 1–2 minutes which expel first the shoulder then trunk and lower extremities. As the body of fetus is delivered a rush of blood stained liquor amni follows, representing the portion of fluid which has been retained in utero along with trunk and limbs.60
Duration of Second Stage of Labor
Duration of second stage is 1 to 2 hour in a primigravidae and 10 to 15 minutes in multipara but it may last very much longer than this when the pains are relatively feeble or with malposition.
In majority of cases the actual time of onset of second stage is uncertain.13 Restricting time limit in second stage of labor to 2 hour for primigravidae and 30 minutes for multiparous women is not uncommon but the evidence does not support it.13,1461
Current debate suggest that arbitrary time limit on second stage should be abandoned, providing there are no fetal or maternal problems and progress is occurring13,14 and early termination of prolonged second stage with instrumental delivery increases maternal and fetal morbidity and does not improve the outcome.
Women Characteristic Behavior in Second Stage Transition
It is a phase that commonly occurs at the end of first stage of labor. Kitzinger (1987)15 suggest that it last a few contractions.
This stage is thought to be most painful and certainly the most distressing for the women. Labor stress hormones are at their peak, which Odent (1999)16 suggest has a positive physiological effect on labor and the women experiences a surge of energy needed to push her baby out.
The diagnosis of the transitional stage moves an observation to higher level as it is a far more women centred and subjective skill. The diagnosis of transitional stage is dependent on knowing the women, her behavior and recognizing any change in her behavior. Progress can thus be diagnosed without need to resort to vaginal examination.17
The women experience the extreme pain of transition, has a decreased ability to listen or concentrate on anything but giving birth.18 The women become frank and honest in vocalizing her needs and dislikes, unfettered by politeness and this should not be misinterpreted as rejection or rudeness by attending person.19
Third Stage or Ejection of After Birth
The after birth consists of the placenta, umbilical cord, and amnion and chorion membrane. When fetus is expelled, there is sudden and striking reduction in size of uterus.62
The fundus of uterus now lies about level of umbilicus and become alternative hard and soft to touch, signifying that intermittent contractions are continuing but they are painless.
As placenta is much less contractile than the placental site to which placenta is attached, placenta separates immediately or very soon after expulsion of fetus with great reduction in surface area of uterus. After an average time period of 10 minutes following observation indicates that placenta is being separated and extruded.
- Uterus becomes smaller and harder, more globular in shape and more freely mobile (Fig. 1.4.2A).
- The level of fundus which is hard and retracted rises while the lower segment, now plainly felt above the pubis is soft and bulging from presence in it of placenta.
- Length of umbilical cord lying outside the vulva is greater than before (Figs 1.4.2B and C).
- A certain amount of hemorrhage is associated with process of separation of placenta, but does not appear at vulva until its extrusion starts.
- Placental expulsion is accompanied by again voluntary effort on the part of the patient. When the placenta appears at vulva and can be withdrawn by obstetrician attendant. It is followed by a certain amount of blood clot expulsion (Figs 1.4.2D and E).
These sequences of changes become more rapid and associated with less bleeding, when an oxytocic is administered late in second stage or at beginning of third stage of labor.
The uterus is now considerably smaller, and should remain almost uniformly firm and hard, but for some hours after labor intermittent spontaneous contraction and relaxation can be recognized.63
Figs 1.4.2A to E: Steps of 3rd stage of labor: (A) Uterus globular and harder with separation of placenta, (B and C) True elongation of umbilical cord, (D) Expulsion of placenta, (E) Confirmation of complete expulsion of placenta and membranes
CONCLUDING REMARK
Understanding physical and psychological signs of onset of labor and its different stages are an integral part of management and conduct of vaginal delivery.
REFERENCES
- Burvill S. Midwifery diagnosis of labor onset. Br J of Midwifery (2002);10(10);600–5.
- Driscoll K, Foley M, Mac Donald D. Active management of labor as an alternative to caesarean section for dystocia. Obstet Gynecol 1984;63:485.
- Walsh D. Evidence based care: part 3; assessing women's progress in labor. Br J of Midwifery (2000a);8(7); 449–57.
- Simpken P, Ancheta R. The labor progress handbook. Blackwell Science: Oxford, 2000.
- Sokol RJ, Stojkov J, Chik L, et al. Normal and abnormal labor progress. IA Quantitative assessment and survey of the literature. J Reprode Med 1977;18:47.
- Hendricks CH, Brenner WE. Cardiovascular effects of oxytocic drugs used postpartum. Am J Obstet Gynecol 1970;108:751.
- Zhang J, Troendle JF, Yanay MK. Reassessing the labor curve in nulliparous women. Am J Obstet Gynecol 2002;187:824
- Alexander JM, Sharma SK, Melintue DD, et al. Epidural analgesia Lengthens the Friedman active phase of labor: Obstet Gynecol 2002;100:46.
- Gurewitsch ED, Diament P, Fong J, et al. The Labor Curve of the Grand Multipara; Does Progress of Labor Continue to Improve with additional child bearing? Am J Obstet Gynecol 2002;186:1331.
- Gurewitsch Ed, Johnson E, Allen RH, et al. The Descent Curve of the grand multiparous women. Am J Obstet Gynecol 2003; 189:1036.
- Ockenden J. The Hormonal Dance of Labor. The Practicing Midwifery 2001;4(6),16–17.
- Walsh D. Evidence Based care part 6: Limits on Pushing and Time in second stage. Br J of Midwifery 2000b;8(10);604–8.
- Sleep J, Roberts J, Chalmers I. The second stage of labor. In Enkin M, Keirse, MJNC, Nailson J (Eds): A Guide to Effective Care in Pregnancy and Child Birth (3rd edn) 2000;289–99, Oxford University Press: Oxford.
- Kitzinger S. Giving birth. How it really feels. Gollan CZ, London, 1987.
- Odent M. The scientification of love. Free Association Books: London, 1999.
- Mander R. The Transitional Stage—Pain and control. The Practicing Midwifery 2002;5(1):10–2.
- Leap N. Pain in labor, MIDIRS Midwifery Digest, 2000;10(1): 49–53.
- Robertson A. Empowering women: Tackling Active Birth in the 90s, Ace Graphics, Camperdown, NSW: Australia, 1996.
Labor room is unique place of hospital, virtually a place of God's creation with its inherent extremes of chaos and confusion, as God is usually in habit of giving its blessings with stern lessons, pain and hard work.
It is ironical that room for operation is called operation theatre while the place for vaginal delivery is called labor room, though the most theatrical up and down occur in “Labor Room.” Labor room is primary, essential and most crucial requisites for any type of setup be it government/private hospital, small nursing homes or peripheral health centers, which provides facility of obstetric care and vaginal delivery to women.
Thus it is very important that labor room should be thoughtfully planned and designed keeping in mind the specific needs of labor unit. In this chapter we will discuss the layout, planning and equipments of labor room.
Planning of labor room should be done keeping in mind that for each laboring women there are two patients to be cared of first mother and second the baby to be delivered and usually there are multiple women to be cared at one time. Secondly there is round the clock work in labor room complex including holidays and Sundays. Planning of good space and annexure helps a lot in smooth management of labor room complex.
A well designed, well equipped and well managed labor room adds greatly to the obstetric outcome of hospital. Some important facts and suggestion for the setup of labor room complex are as follows:66
LOCATION OF LABOR ROOM
Obstetric patient come to hospital in different stage of labor and some times in critical situations like hemorrhage, fits, malpresentation. Labor room should preferably be located on ground floor of hospital. As it is safe, comfortable for patient and time saving.
It should have smooth and broad galleries and doors at all entry and exit points and preferably closely connected to pre-labor ward and cesarean operation theater for quick transfer of women in critical situations.
If possible working direction of labor room should be directed towards sunlight with one wall made of gazed glass. It enhances illumination of labor room, helps in day time working and has a positive psychological effect on patient as well hospital staff.
SIZE OF LABOR ROOM
Dimension of labor room should be planned keeping in mind, the approximate number of deliveries in hospital and its future possible workload and whether hospital is giving services for high risk obstetrical women or providing delivery facilities for only low risk women. However, it should be kept in mind that at any time low risk women can develop sudden complications.
One should plan beforehand the types and number of labor tables, and other equipments, their possible dimension relative to area of labor room; so that there is no crowding of space after wards. In labor room there must be provision of a good running space in between and at both ends of labor tables for smooth functioning.
Beside main labor room adequate provision should be made for different annexure of labor room that is pre-labor ward, scrub room, wash area, sinks and adjoining doctors/senior sister's room.67
American Academy of Pediatrics and American College of Obstetricians and Gynecologists (2002)1 have collaborated in development of guidelines for prenatal care. (Table 1.5.1) notes directives of space and personnel requirement for conduct of normal labor.
EQUIPMENTS
Equipments and instruments are crucial part of obstetrics. The desired equipment in a well functioning labor room is enlisted in (Tables 1.5.2 and 1.5.3; Fig. 1.5.1).
AAP and ACOG (2002) recommendation of minimum room dimensions for labor room and delivery are summarized in Table 1.5.1.
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Out of these some major equipments requires special mention.
Labor Table/Berthing Bed
Nowadays wide variety of berthing beds and tables are available. Very costly labor table are usually not needed but before purchasing one should observe certain feature carefully.
Labor table should be of adequate size so that patient can lie comfortably before and after delivery in any position.69
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Moreover, labor table should have facilities for quick change of position in all direction, i.e. head high, head low and lateral tilts. Change of position can be done manually, by hydraulic system, electrically or electronically operated system. Hydraulic and electronically operated systems are difficult in maintenance and repair while electrically operated systems are quick, convenient and very easy in maintenance. Labor table should have facility for side support so that patient may not fall in conditions like convulsion, hypovolemia. Lithotomy stirrups should have preferably padded support both on knee and ankle joints. Facility of inbuilt IV drip stand, bucket, support handle for bearing down are optional feature of labor table, which enhances the functioning capacity of table (Figs 1.5.2A and B).70
Light for Labor Room
Good illumination in labor room need special attention as it plays significant role in obstetric management. Main illumination lights should be connected to UPS system which stabilizes voltage and on line electricity supply remains uninterrupted. Beside this invertor facility for few lights should be there. A ceiling shadow less cold light source provides good illumination for two adjacent labor tables. Beside this a shadow less focusing cold light on stand should always be available. It helps a lot in repair of high cervical, vaginal tear or deep episiotomies. There should be provision of adequate number of tube lights. Sun light passing through glazed glass windows also adds to background illumination.
Boyle's Anesthetic Trolley
Fully equipped and working anesthetic trolley should be an integral part of major equipments of labor room. Obstetric maneuvers like manual removal of placenta, assisted delivery in malpresentation, etc. require general anesthesia. Beside this high risk women like patients having moderate to severe anemia, severe PIH or postpartum hemorrhage require full cardio respiratory support (Fig. 1.5.3A).
Maternal Monitoring Equipment
Pulse oxymeter and cardiac monitor add to the safety profile especially in high risk obstetrics. It is a great aid in anticipation as well monitoring of maternal condition in high risk obstetric patient like heart disease, severe anemia, severe PIH, There are equipment available which have combined facility of fetal cardiotocography and maternal pulse oxymetry (Fig. 1.5.3B).72
Neonatal Resuscitation Station
Neonatal resuscitation station is one of the most important part of labor room and should never be compromised. Pediatric stethoscope, radiant heat warmer, facility of low pressure neonatal suction machine, Amboo bag with mask of different sizes and oxygen supply, pediatric laryngoscope and endotracheal tubes are minimum essential requirement for labor room.
Full fledged neonatal resuscitation unit with CPAP provide all facilities of temperatures, humidity control with cardio respiratory support at one step. Initially these units appear costly, but in long term they help a lot in improving neonatal salvage rate (Figs 1.5.3C and D).
Fetal Monitoring Equipment
Two good quality stethoscopes, portable fetal Doppler is essential requisite for labor room. However, fetal electrocardiotocography machine aids a lot in decision making in obstetrics and a real cost effective equipment of labor room (Fig. 1.5.3E).
Crash Cart
Crash cart is specific trolley having, multiple drawers and place of keeping oxygen gas cylinders. In crash cart emergency life saving drugs, oxytocic drug, suture material, IV fluid, plasma expanders, antihypertensive, diuretic, anticonvulsant drugs should always be kept in specific well leveled drawers for optimum use.
Emergency patient and emergency situation often appear in labor room unwarned. Quick and systemic availability of drugs, IV fluids saves the patient and day many times (Fig. 1.5.3F).73
Figs 1.5.3A to F: (A) Boyle's trolley with cardiac monitor, (B) Combined fetal and maternal monitor, (C) Neonatal resuscitation radiant heat warmer, (D) Baby weighing machine and instrument to receive the baby, (E) Cardiotocography machine, (F) Crash cart
Sterilization Equipment
Autoclave and boiler should be separate for labor room for quick sterilization which is often needed in a busy labor room. Even in the hospital where there is central sterilization, labor room should preferably have its own sterilization unit. It makes the staff responsible and self reliant.
Cupboards
Provision of adequate number of cupboards with and without lock should be made in labor room to keep reserve cotton/gauge/for sterilization and cleanup, patient's gown, baby sterilized cloths, (if they are being provided by hospital), stationeries (case sheets, consent forms, blood requisite form, and investigation form), Soaps, washing materials, sterilization material, emergency delivery drug sets, for emergency admissions and extra stethoscope, fetal doppler, extra BP instruments.
Availability of cupboards and more so availability of things at fixed place helps a lot in smooth functioning of labor room.
Slab
Slabs of adequate size made of good quality marble or granite should be made, at comfortable distance from labor table for keeping all cadys with instruments, linen, gauge cotton, etc.
Annexure (Additional) Facilities in Labor Complex
Labor room is a place where twenty four hours in a day and 365 days in a year work is going on. Beside this child birth is a messy and bloody business so it require certain facilities for the patient, attendant and hospital staff, close to labor room. These are as follows:75
Pre-labor Ward
A pre-labor ward close to labor room should be an integral part of labor unit. In pre-labor ward the women in latent and first stage of labor are managed under close observation. Patients are shifted to labor room only in late second stage of labor.
In this ward close relatives are allowed for moral support and relaxation. Women are allowed to walk or assume position of their comfort. Staff skilled in fetal monitoring and management of first stage of labor are focused in pre-labor ward. The informal and friendly environment, conversation and contact with fellow laboring women, helps a lot in a alleviating fear and anxiety of patients. It should have 3–6 bed according to hospital need with I/V drip stands with adjoining bed side lockers, oxygen, suction facility with equipment of fetal and maternal monitoring equipment.
Emergency Obstetric Room
If possible there should be an emergency obstetric room close to labor room in which critically ill patient or high risk obstetrical patients can be kept. It helps in isolation, more intensive monitoring and focused management of patients. In this room there should be equipment for maternal resuscitation. Preferably bed should have adjustable facility for lithotomy position. Room should have enough space for minor obstetric procedure, which can be of great help in management of women with ecclampsia, antepartum hemorrhage or post delivery observation in case of any complication.
Scrub Room
Labor room should have adjoining scrub room for pre surgical wash up of obstetrician and paramedical staff.76
Habit of good scrub and surgical precaution on the part of labor unit staff helps a lot in long way to reduce many obstetrical short and long-term complications. Scrub room should have facilities of two tap of good qualities with sink of adequate depth and good drainage for simultaneous wash up of two people, geyser, hooks for plastic aprons, gowns and lockers for keeping valuable and belongings.
Wash Areas
Adjoining wash area and sinks for fast cleaning of equipments, linen and room, helps a lot in making labor room neat and clean and rapid functioning of paramedical staff.
Doctor/Staff Room
Doctor/senior staff room should be close to labor room and pre-labor ward. In labor room and pre labor ward close monitoring of mother and fetus is required. Beside this usually the working hours are long and obstetrical work is strenuous. A comfortable place for relaxing and waiting increases the efficiency of staff. It also has positive effect on mood and behavior of staff working in labor room who are usually blamed for rudeness by relatives and women. Staff room should have preferably an attached toilet, sofa cum bed, lockers and cupboard for valuable and belonging, small table with 2–3 chairs. So many times, all of us tend to forget that medical personnel are also human being and in between work, space for a nap, snack or light talk, make work more enjoyable.
Number of persons desired for smooth functioning of labor room is listed in Table 1.5.4. Recommended nurse to patient rates for labor and delivery is summarized in Table 1.5.5 (ACOG 2002).177
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Proposed map of labor room unit is depicted in Figure 1.5.4.
CONCLUDING REMARKS
Labor room is the most essential and lively place of obstetric working with all its inherent pleasures, dangers and complications of child birth. Availability of a well equipped and well managed labor room is one of the real difference between domiciliary and institutional delivery. Mind and money invested in planning the design of labor room complex, placement of good quality equipments and smooth management of labor room can make the vaginal delivery more safe and satisfying experience for women, relatives as well hospital staff.78
Fig. 1.5.4: (1) Labor table, (2) Boyle's anesthetic trolley with pulse oxymeter, (3) Fetal cardiotocography machine,(4) Radiant heat warmer and neonatal resuscitation unit,(5) Crash cart, (6) Place for anesthetist, (7) Slab for cadys, (8) Instrument trolley, (9) Shadow less light Annexure: (10) Wash area (11) Doctor's room, (12) Pre-labor ward
Knowledge, skill and experience of obstetrician always require well illuminated, clean and comfortable labor room with well maintained equipments. It is duty as well right towards our patients and ourselves.79
REFERENCES
- American Academy of Paediatrics and American College of Obstetric and Gynecologist; Guideline for Perinatal Care (5th edn). AAP & ACOG Washington DC; 2002.
1.6. RECORD KEEPING IN LABOR MANAGEMENT
Medicolegal claims in obstetrics are increasing and litigation experts advise that any surgical or obstetrical practice is likely to be judge as being only as good as their written notes.1
Standard of record keeping should be learnt and maintained. It is not an uncommon thing to see grossly incomplete case record or writing too much yet missing important recordable aspect of care.2
All possible medico legal issues to be kept in backdrop of mind while making protocols for record keeping in obstetric patient. Records including all essential notes, test results, prescription cards, medicine, and admission time should be retained for 25 years.
INFORMED CONSENT
Informed consent to be taken by the person who is of sufficient mental capacity to make the decision and possess all the important, relevant information.3
Performing any invasive or intimate procedure requires maternal consent and doctor/midwife should document if this has been given, e.g. if AROM or oxytocin induction to be done, the client should be informed of the indication and possible benefit as well risk and complication of the 80procedure. Only then women can make an informed decision and thus give or and withhold consent.
Basic Standard of Record Keeping are:
- Written legibly in black/blue, water resistant ink.
- Date, time and sign all entries with name written on first entry and subsequent pages.
- All referral and consultation should be noted detailing the name and status of the person.
- One should try to avoid abbreviation or ambiguous term.
CONTENT AND QUALITY
Note should contain information about:
- Physical condition of patient,
- Psychological well being,
- Care given,
- Brief points about information given, if consent was given and any procedure carried out,
- Document the time and persons to whom referral has been made and time that they responded and attended,
- One should document decision including decision to wait and see.
A lack of documentation in wait and watch decision can make it appear as if no decision has been taken.4 If treating doctor advise operative interventions and patient relative refuse for that or opt for wait and see, than this must be documented as consent in the own handwriting of consent giving person, which explain that all the risk have been explained to them if operative intervention is deferred and they have decided to wait and see. This must again be properly signed, and attested with witness signature.81
Some significant points often overlooked in obstetric case record:
- When describing liquor, the midwife/doctor should mention its color and approximate quantity—minimal/moderate or large amount and also making a note if all appears normal.
- In documentation of minimum meconium staining of liquor, one should see to clarify if it is thin or sparse or of greater concern, i.e. thick/fresh.
- One should be vary clear to comment when things and findings are straight forward, e.g. if cardiotocography is normal, then one should document it.
Alteration in Records
- Incorrect entries should be surrounded by bracket and one line drawn through the text followed by writing “Incorrect entry” and signing it.
- One should not use corrective fluid or scribble out.
Time and Late Entries
It should be clear at what time event occurred and what time entry was made.5 All time should be entered in the margins using the 24 hours clock. All clinician making entries in the notes should use the same clock.
CTG tracing should clearly state the – name, date and time.
CONCLUDING REMARKS
Case record will be relied upon heavily in a legal investigation. Given the unexpected nature of legal claims, staff that fails to keep clear, contemporaneous records, particularly in the labor ward, may be putting their heads in a noose.82
It may be difficult to maintain a good standard of record keeping when the unit is extremely busy, when emergencies occur, but there is a clear duty to make adequate entries in the case notes as soon as it is practicable.4
REFERENCES
- Mason D, Edwards P. Litigation: A Risk Management Guide for Midwives, Royal College of Midwives (RCM): London, 1993.
- Andrews S. Clinical Risk Management study Drug Review (RCM), London, 2002.
- Griffth R, tengnah C, Gray R. Consent and Women in Labor; A Review of the Issue. Br J of Midwifery 1999;7(2),92–4.
- Symon A. The Standard of Case Records. Br J of Midwifery 1997;5(8),462–4.
- Byrne U. Record Keeping: a risk management perspective. Br J of Midwifery 1999;7(7):436–9.