Physiology of pregnancy

The hormones with the strongest influence on pregnancy are HCG, estrogen, progesterone, HCS. These are secreted primarily by the placenta, but the corpus luteum is an important source of hormones in first 7-12 weeks.

Adjustment to pregnancy

Digestive System, Nutrition and Metabolism

morning sickness
- one of the first sign of pregnancy
- the cause is still unknown but there are several hypothesis.
- Hypothesis 1: reduced intestinal motility caused by steroid of pregnancy
- Hypothesis 2: evolutionary adaptation to protect fetus from toxin. Fetus is most vulnerable to toxin at the peak of morning sickness. Women with morning sickness tend to prefer bland food rather than spicy and pungent foods which are toxic to the baby

Constipation and heartburn
- Constipation: result from reduced intestinal motility
- Heartburn: result from enlarging uterus pushing upward on stomach, causing the reflux of gastric contents into the esophagus

Increase basal metabolic rate
- Thus pregnant mother often feel hot
- Appetite might be strongly stimulated ,causing mother to overeat when they only need an extra 300kcal/day.

Nutrition
- During last trimester, fetus needs more nutrients than the mother digestive tract can absorb. In preparation to this, the placenta stores nutrients early in gestation and release them in the last trimester
- Nutrition such as iron, calcium, vitamin K and D as well as folic acid are important for the development of fetus

Circulatory System
- The mother blood volume will rises about 30% during pregnancy because of fluid retention and hemopoeisis to supply blood to the placenta for the fetus
- Cardiac output rises about 30% to 40% above by 27 weeks and return to normal in the last 8 week
- Uterus puts pressure on the large pelvic blood vessels. It interferes with the venous return thus cause varicose vein, oedema and hemorrhoid

Respiratory System
- minute ventilation increase about 50%
- this is because: 1. oxygen demand are about 20% higher to supply the fetus and support the mother increase metabolic rate. 2. progesterone increase sensitivity of respiratory chemoreceptors to carbon dioxide and ventilation is adjusted to keep the arterial co2 at low level. 3.expanding uterus push the abdominal viscera up towards the diaphragm and interferes with the normal breathing

Urinary System
- aldosterone and steroids of pregnancy promote water and salt retention by kidneys. GFR increase by 50% and urine output is slightly elevated so that the mother can dispose of both her own and fetus metabolic waste.
- Expanding uterus also compress on the bladder reducing its capacity, the urination become more frequent and mother might experience uncontrollable leakage of urine

Integumentary System
- skin must grown to accommodate the expansion of the abdomen and breasts and added fat deposition on the hips and thighs/
- stretching of dermis can always cause striae or scretch marks
- melanocyte activity increase in some areas and darkens the areolae and linea alba. The latter often becomes a dark line ‘linea nigra’ a line from umbilical to pubic region.
- Some mother also require temporary blotchy darkening of the skin over the nose and cheeks called the ‘ mask of pregnancy’