Uterus: An OverviewChapter 1

Like all other organs of the body, it does not have to function from birth till death. It has only got function for certain point of time in the life of the woman and that function lasts from menarche to menopause. Every month, it prepares itself for implantation, if implantation occurs, it remains quiescent. When the time comes for expulsion, it becomes active. In the mean time, it increases in size-shape and volume, and after expulsion, within six weeks, it comes back to its original, shape, size and volume and starts preparing again for another implantation. More over, during pregnancy, the different parts of the same organ behaves differently. All along pregnancy the cervix must remain closed to take the pregnancy to term and when the expulsion time comes, it must dilate and dilate beautifully, other wise it is a bad organ. After menopause, it becomes the organ of woo of many women. This is the uterus for you.

There is little information in Greek writings about human anatomy; however, Herophilus (4th century BC)' the great anatomist in Alexandria and the originator of scholarly dissection, recorded the different positions of the uterus. Soranus of Ephesus accurately described the uterus (probably the first to do so), obviously from multiple dissections of cadavers. He recognized that the uterus is not essential for life, acknowledged the presence of leiomyomas and treated prolapse with pessaries.⁴

Galen's neat idea of the uterus as an interior scrotum notwithstanding, most medieval medical practitioners believed the uterus to be a distinctly female organ that caused a host of specifically female diseases. “The uterus is called also matrix because it is the mother of all,” wrote John Moir in 1620. It was a cold and dry organ. Less attractively, some proposed that the uterus was a “sewer” - a site of noxious poisons that caused diseases such as the “suffocation of the mother,” a condition in which the womb wandered throughout the body and which the Greeks described as hysteria. No equivalent male organ could be found that affected the body so dramatically.

By the late 15th and early 16th centuries more naturalistic images of the human body resulted from a growing interest in the human form by artists such as Leonardo Da Vinci (Fig. 1.1).⁵

The uterus was also the site of a great deal of reproductive speculation. For centuries, its structure was thought to reveal the mysteries of the number and sex of its offspring. “It is hollow and villous within, smooth outside, divided into seven cells, and has two openings,” wrote Master Nicolaus, reflecting the standard view that the womb had as many divisions as the days of the week and could yield a maximum of seven children at a time. Mondino de' Liuzzi affirmed this idea in 1316. Others divided the womb simply into two parts, arguing that males were born on the right side and females on the left. “Woman was endowed with two wombs,” wrote Moses Maimonides in the late twelfth century, arguing that they corresponded to the number of breasts. Many insisted on a central cell in which hermaphrodites were born. Finally, anatomists argued for the presence of uterine horns, an error that arose from dissecting animals. Several key developments altered the traditional images of the reproductive organs. Vesalius and his followers began to give more physical specificity to the human uterus. Initially, Vesalius in 1543 prominently displayed the uterine horns - he described them as “two blunt angles which resemble the immature horns on the foreheads of calves” - but he began to wonder why they, like the cells of the uterus were so difficult to see. In the 1570s, Laurent Joubert stoutly contradicted the idea of the womb “being divided in two in the manner of animals” or having “booths separated one from another.”⁶

Ramsay has reviewed the history of the evolution of knowledge concerning the anatomy of the uterus. She observed that during the Middle Ages the popular theory was the uterus was multicompartmental. The most popular number of compartments was believed to be 7. In 1315 Mondino dei Lousie conducted the first authorized public dissection of a human body and from his findings the uterus, cervix and vagina were described almost as we know these structures today. Leonardo da Vinci correctly depicted the anatomical relationship between the ovaries, tubes and ligaments. He considered the uterus to consist of a single cavity. About the same time Beringario da Carti stated that it is a pure lie to say that the uterus has 7 cavities. Vesalius first used the term uterus in his treatise De Humanie Corporis Fabrica. Since that time we have come to understand the organ in greater detail.

In the non-pregnant state, the uterus is entirely in the pelvis. It is a hollow pear shaped muscular organ and has three parts; the fundus, body and cervix. The part of the uterus above the insertion of the fallopian tubes is termed as the fundus. The area of insertion of the tubes is known as the cornua. Just anterior to the fallopian tube, the round ligament runs from the uterus to the inguinal rings. Behind the fallopian tube is the ovarian ligament, which attaches to the ovary. The uterine cavity communicates with the peritoneal cavity via the fallopian tubes and with the vagina via the cervical canal.

Anteriorly the uterus is related to the bladder and posteriorly to the rectum. The peritoneum covers the body of the uterus and the supravaginal portion of cervix posteriorly. From there, it is reflected over the rectum, forming a pouch called the rectouterine pouch or pouch of Douglas. Anteriorly the peritoneum covers the body and is then reflected onto the bladder at the level of the internal os, creating the loose uterovescical fold. Laterally it spreads forming the leaves of the broad ligament. The uterus has three layers, the outer serous layer or perimetrium, the middle muscular layer or myometrium and the innermost mucous layer called the endometrium. The endometrium is a single layer of columnar epithelium. The endoemtrium responds to hormones and undergoes cyclical changes during the menstrual cycle (Fig. 1.4). The normal disposition of the uterus is anteverted and anteflexed so that its weight is largely borne by the urinary bladder. It also receives passive support from the cardinal ligament and active support from the muscles of the pelvic floor. The uterus may assume other dispositions like excessive anteflexon, anteflexon with retroversion, retroflexion with retroversion.

Over the nine months of pregnancy, the uterus expands greatly to accommodate the fetus becoming larger and increasingly thin walled. At the end of the pregnancy, the uterus drops because of the engaged head, the fundus dropping below it's highest level, i.e. costal margin. Immediately after delivery, the large uterus becomes thick walled and edematous, size reducing rapidly. During menopause, the uterus again reduces in size. In postmenopause, it regresses to a markedly smaller size, once again assuming childhood proportions.

Labour represents a fraction of the total time between conception and birth, perhaps 1/1000 and the rest of the time, the fetus grows and develops to adopt itself for its independent existence. While labour proper is generally a process taking a few hours, its onset is far from being sudden. It is the culmination of a gradual process which has been evolving over several weeks and named pre labour by Demelin (1927).⁸

Then comes latent labour, whose starting point is not known, after which the active phase of labour starts. To diagnose labour, the classical definition ‘Uterine contraction that bring about demonstrable effacement and dilatation of the cervix,’ does not help as the diagnosis is confirmed when labour has actually commenced. It is usually a self diagnosis, known by patient's version and both are fallacious.

Assuming that the labour had begun, what are the expectations of or the progress of normal labour?

The dictum of normal progress of labour is changing over the years. Few years back the dictum was ‘never allow the sun to set twice on a woman in labour’ to ‘don't allow the sun to set even once on a woman in labour.’ ‘Masterly inactivity and watchful expectancy’ to ‘act fast, don't delay, finish soon, delay is dangerous.'

In 1954 Friedman⁹ had his pioneering study, the graphic approach. This helped to dispel many myths about labour and placed the treatment of dysfunctional labour on a more logical basis. Graph has got three divisions, preparatory, dilatation, and pelvic. Active has got three components-acceleration phase, phase of maximum slope and the deceleration phase.

Accurate determination of both the onset and the end point of the latent phase is obviously important. Unfortunately neither end is clearly discernible. In the beginning of latent phase, onset of true labour is not clear-cut.

Other authors have questioned much of Friedman's work. Philpott and Castle, O'Driscoll et al and Studd,^10–13 have all tended to disregard the latent phase of labour, at least as far as the practical management of labour is concerned as in different parts of the world, the majority of patients arrive at hospital in labour with the cervix at least 2-3 cm dilated. In the clinical management of labour it is usually not possible to divide the active phase of labour into the three subdivisions suggested by Friedman.

What is practical and reasonable is to expect the normal patient to make progress of 0.5-1 cm/hour in labour. Philpot has introduced two lines in the graph, Alert line and Action line to depict deviation of cervical dilatation towards abnormal.

He also devised the partogram, where in a single sheet of paper all the data about the mother, fetus, 7and the progress is recorded. On the same principle WHO Model of partograph was prepared (1993)¹⁴.

Alert line starts at 1 cm cervical dilatation in 0 hr and ends at 10 cm in 9 hrs.

The action line is drawn 4 hrs to the right and parallel to the action line.

Labour is considered dysfunctional when cervicograph crosses the alert line and falls in zone 2 and intervention is required when it falls on zone three.

WHO (1994) recommended partograph in all labour cases, which has shown to reduce the incidence of prolonged labour and the rate of LSCS with improvement of maternal morbidity and fetal morbidity and mortality. More over, partogram facilitates hand over of the case, and responsibility and accountability of the person conducting labour.

In spite of its utility, and though 54 years is past, most of us, to speak none of us are using it continuously in our labour cases. Its use is sporadic. The question raised is why and the answer is simple, we are not habituated with graphs and charts. As soon as we examine a case, we form in our brain a time when this woman should deliver. When she crosses that time we start worrying ourselves. Now Dr AK Debdas from Jamsedpur has come out with paperless partograph. It is nothing but putting our mental time of delivery on the front page of the admission card on writing.

Reynolds and coworkers¹⁵ emphasized that uterine contractions of normal labour are characterized by a gradient of myometrial activity being greatest and lasting longest at the fundus and diminishing towards the cervix. Caldero Barcia advanced the work of Reynolds and reported that there was a time differential in the onset of the contraction in the fundus, midzone and lower uterine segment.

Larks described about the pacemaker wherefrom the excitation waves start then joining and sweeping over the fundus and down the uterus. Caldero Barcia and Poseiro(1960)¹⁶ from Montevido, Uruguay introduced the concept of Montevideo units to define uterine activity. This unit is equal to the product of the average intensity of uterine contractions above base line tone, multiplied by the number of contractions observed during a 10 minute period of monitoring. It is expressed in mm of Hg per 10 minutes (Figs 1.5 and 1.6).

The other methods available are, Alexandria Unit, Uterine activity Unit, and uterine activity integral, out of which the most commonly used one is Montevideo unit.

A steady rise in uterine activity occurs during the first stage of labour from approximately 120 Monteivideo units per ten minutes to 180 units or more and approximately the same in primi and multi at comparable stages of cervical dilatation.

The current recommendations of the American college of Ob/Gyn are that uterine activity producing 200 or more Montevideo units in a 10 minute period should be present for at least 2 hours before the diagnosis of failure to progress or arrest of active labour is made.

Many methods are available to measure the uterine activities, they may be internal (invasive) or external (non-invasive):

Inefficient uterine activity in its turn may be: (1) Coordinated uterine action (Hypoactive) or Incordinate (Hyperactive) the hyperactive uterus may be totally hypertonic or Colicky, or having hypertonic lower uterine segment, or constriction ring dysfunction. Cervix sometimes may not perform normally resulting in Cervical dystocia.

Pathophysiology of myometrium is dealt extensively in other chapters.

Increase in intracellular calcium is the important signal to cause myometrial cell to contract. Intracellular and extracellular acidification reduces or abolish the phasic contractile activity and these effects can be accounted for by changes in intracellular calcium concentration. In dysfunctional labour, the pH is reduced, lactate levels in the blood is increased, capillary oxygen saturation are significantly lower. This supports the hypothesis that myometrial capillary blood is more acidic in women labouring dysfunctionally and that this causes the reduction in contractile activity via a reduction in intracellular calcium. The future aim is to discover, why when intermediate hypoxia occurs in all labouring women, only some become acidotic and labour dysfunctionally. The better understanding of pathophysiology will improve the management.

As regards management of inefficient uterine action, the general resuscitative measures like fluid balance, etc. to be taken care of and a fresh review of the case to be done.

Hypotonic dysfunction, the most common uterine dysfunction, is managed by active management of labour advocated by O' Driscoll¹⁷. It is based not on an idea of normal labour, but on the idea of minimal risk labour. Active management implies sensible anticipation of the patients progress in labour. The complications of prolonged labour, dehydration, ketosis are reduced, reduces the work load of the ancillary staff, reduces the primary cesarean section rate, reduces the maternal morbidity, mortality and the fetal morbidity and mortality, converts one of the most important time in a family's life into a safer situation, physiological facts are translated to measured parameters, these facilitates analysis and better obstetric judgment. Treatment consists of reassururance, amniotomy and, oxytocin infusion.

I myself advocate active management of labour.¹⁸ The conclusion drawn from my study was first stage of labour reduced significantly, the second stage of labour is also reduced though statistically not significant. The CS rate was reduced significantly and whenever the decision was taken, it was taken early so that the maternal and fetal morbidity was less and there was nil mortality

Hypertonic dysfunction is less common than hypotonic dysfunction. The condition is managed by stopping the oxytocin drip and sedating the patient. Once the patient is well sedated, oxytocin drip may be started again with low dose, but it should be used with close supervision.

Magnetic resonance imaging (MRI) is now playing an increasing role in the evaluation of myometrial abnormalities, because of its greater intrinsic soft tissue contrasts than either computed tomography (CT) and ultrasound. The multiplannar capabilities of MRI becomes particularly important for imaging the myometrium because of the variable orientation of the uterus. It shows soft tissue contrasts between smooth 9muscle proliferation and the surrounding myome-trium. The diagnosis of adenomyosis has become possible preoperatively due to MRI. On MRI adenomyosis appears as a poorly defined mass with decreased signal intensity similar to and often blending with the junctional zone.