Pregnancy Medicine Alaka K Deshpande
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PregnancyChapter 1

Alaka K Deshpande
Pregnancy is an amazing and fulfilling life event. When a woman conceives, she is called as a pregnant mother. Each and every event/life situation in relation to a pregnant mother; one is always concerned for—
  • The mother
  • The fetus, and
  • The pregnancy outcome.
Pregnancy is a physiological event averagely of 40 weeks duration.
The mother's body prepares to bring in the new life—the baby. The mother's body undergoes extensive morphological changes, physiological adaptations and emotional alterations.
Any aberration in any of the three factors complicates the pregnancy.
The challenges to the clinician vary from time to time related to the duration of pregnancy which is broadly classified as first, second and third trimester.
 
MORPHOLOGICAL CHANGES
 
Reproductive Tract
Normal non-pregnant uterus is a small solid organ, weighs about 70 gm. with a cavity of 10 ml or less. This structure has to adapt to accommodate the products of conception namely the growing fetus, the placenta and the amniotic fluid. As a result, during pregnancy, it enlarges in size, appears to be a thin-walled organ with adequate capacity to accommodate the fetus, placenta and the fluid.
It enlarges with hypertrophy of the muscle cells and stretching. The production of new myocytes is limited. Accumulation of fibrous tissue and considerable increase in elastic tissue is noted.
The enlargement is most marked in the fundus. In early pregnancy, it maintains its pear shape but as pregnancy advances, it assumes a globular form becoming spherical by 12 weeks. At this stage, it becomes too large to be accommodated in the pelvic cavity so it rises above the symphysis pubis and becomes abdominal. As it grows, it pushes the intestines laterally and superiorly, contacts the anterior abdominal wall. In late pregnancy, it almost reaches the liver.
The uterine wall becomes thinner as pregnancy advances, at term, it is about 1.5 cm. The uterus transforms into a muscular sac, with soft and thin wall which can be indented easily during palpation of the fetus.
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The original cavity of 10 ml volume now accommodates a volume of 5 liters (may be 20 L or more). So there is 500- to 1000- fold increase in volume compared to non-pregnant uterus. The anterior abdominal wall supports the uterus. When the woman is supine, the uterus rests on the vertebral column and the great vessels, particularly, inferior vena cava causing edema in feet at term.
A 70 gm organ, at term, weighs about 1100 gm. Mainly the stimulation by estrogen, perhaps progesterone, and partly the mechanical distension cause these changes.
Cervix: As early as first months of gestation, the cervix begins hypertrophy. There is hyperplasia of the cervical glands. Increased vascularity and edema result into softening of the cervix with a cyanotic hue. The changes are estrogen induced.
Ovaries: Ovulation ceases during pregnancy.
Vagina and perineum: In preparation for the distension during labor, the vaginal walls undergo changes. The increased vascularity gives a characteristic violet color to vagina. The mucosal thickness increases, there is loosening of the connective tissue and hypertrophy of the smooth muscle cells. The volume of cervical secretion increases during pregnancy.
Breast: By the end of the second month, the enlargement of the breast is seen. Breasts increase in size. The woman may experience the breast tenderness. The nipples become considerably larger, more erectile and deeply pigmented. The areolae become much larger and deeply pigmented.
At term, the uterus holds a fetus of 3400 gm, placenta of 650 gm and amniotic fluid of 800 gm.
Theses morphological changes regress after the delivery. The uterus involutes. After cessation of breastfeeding, the size of the breast decreases. The pigmentation remains.
 
PHYSIOLOGICAL ADAPTATION
Body weight: The body weight increases, most of it due to—
  1. Uterine contents
  2. Expansion of plasma volume, and
  3. Expansion of extra-vascular space.
The weight gain at term is due to—
Fetus
3.4 kg.
Placenta
0.650 kg.
Amniotic fluid
0.8 kg.
Uterus
0.97 kg.
Breast
0.40 kg.
Blood
1.45 kg.
Extravascular fluid
1.480 kg.
Maternal fat
3.345 kg.
Total
12.5 Kg.
Increased water retention is a physiological alteration in pregnancy.
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Carbohydrate, Fats and Proteins
In normal pregnancy, there is mild hyperinsulinemia resulting into mild fasting hypoglycemia, postprandial hyperglycemia.
Proteins: The products of conception are relatively rich in protein contents indicating more efficient use of dietary proteins.
Body fat components increase appreciably during pregnancy. Maternal leptin levels progressively increase during pregnancy.
Lactation speeds the rate of decrease of many of these components.
Blood volume: Pregnancy-induced hypervolemia is observed. The expansion may be 40 to 45 percent above the non-pregnant level.
Increased erythropoietin levels in the mother result into increase both in erythrocytes and plasma.
The functions of this hypervolemia are:
  1. To meet the demands of increased vascularity of the uterus.
  2. To protect the mother and the fetus against deleterious effects of impaired venous return in supine and erect position by the gravid uterus.
  3. To safeguard the mother against parturition associated blood loss.
Electrolytes: During pregnancy about 1000 mEq of sodium and 300 mEq of potassium are retained although the serum concentrations remain within normal limits.
The serum calcium is low probably due to lowered serum albumin levels.
The magnesium levels also decline. The developing fetus imposes increased demands on the maternal Ca and Mg. In third trimester about 200 mg of calcium is deposited in the fetal skeleton.
Appropriate dietary supplements to the mother are essential.
The vascular resistance decreases, so arterial blood pressure is lower. There is increase in the cardiac output. The heart rate increases by about 10 beats/min.
The diaphragm is pushed above by about 4 cms. by the gravid uterus.
Lung compliance is unaffected. The tidal volume, minute ventilatory volume and minute oxygen uptake increase significantly.
The abdominal viscera, particularly, intestines are displaced. Dyspepsia, gastroesophageal reflux disease (GERD), are common. Hemorrhoids are fairly common during pregnancy and are largely due to elevated venous pressure below the level of the gravid uterus.
Glomerular filtration rate increases by 50%. Endocrine system shows appropriate changes with increased levels of prolactin, increased concentration of thyroxine-binding globulin (TBG) which raises the total thyroxine levels. Estrogen levels remain high.
All the systems show adaptation for this act of creativity.