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Physiological changes during pregnancy

There are numerous physiological changes that occur during the pregnancy. I will highlight some of the changes here that seem to bother more patients.

Skin and breast changes

  • Linea nigra - Pigmentation appears progressively darker over the midline of the abdominal wall. This progressively gets lighter after delivery but tends to be visible still if one looks hard for it in most patients.

  • Striae gravidarum - These are stretch marks that appear over the abdominal wall and sometimes thighs. Various stretch mark creams have been used to attempt to reduce these stretch marks. These may work in some patients.

  • Breasts become bigger during pregnancy as they prepare for breastfeeding after pregnancy. Continue to do self-check monthly for lumps in the breasts during pregnancy as hormonal changes during pregnancy may stimulate pre-existing lumps in the breasts to grow larger and hence become more noticeable, or stimulate new growths in the breasts. The nipples do appear larger with Montgomery tubercles and become darker. If the nipples are inverted, you may wish to use nipple pumps in the third trimester to evert the nipples to prepare for breastfeeding.

Gastrointestinal changes

  • Morning sickness with nausea and vomiting is common during pregnancy, peaking at 8-10 weeks and starts to improve from 10 weeks and eventually resolving by 12-16 weeks. Small frequent meals or careful choice of food may improve this symptom. Medications like metoclompramide may be useful in moderate cases. Admission for stronger medications and intravenous fluid transfusion may be required when dehydration becomes severe.

  • The stomach takes a longer time to empty its contents as the muscle junction between the stomach and the small intestine tends to be tighter.

  • Acid reflux is common as the muscle junction between the stomach and the oesophagus is more relaxed, and increasing size of the uterus may further compress on the stomach contents. Sitting upright after meals, antacids and medications to reduce acid production may be useful to treat this symptom.

  • Decreased movement of the large intestine which may lead to increased water retention and constipation.

Musculoskeletal changes

  • Body posture changes with the back arching more forward to keep the pregnant body with an enlarging uterus in balance. This places stress on the back muscles. Backache, hence, is common during pregnancy.

  • Certain skeletal joints become more lax during the pregnancy. The symphysis pubis (which is the joint in the front of the pubic bones) commonly causes pain ranging from mild to severe especially during the third trimester of pregnancy. The hip joints undergo the same changes. These are difficult to treat and may impair mobility to varying extents.

Hormonal changes

  • Increasing beta human chorionic gonadotropin (bhCG) levels in the first trimester has been thought to be the cause of morning sickness in most patients.

  • Increasing progesterone levels

  • increase the rate and depth of breathing causing a sensation of difficulty in catching one's breath occasionally

  • in the third trimester predispose susceptible pregnant women to developing gestational diabetes mellitus.

Heart, blood vessels and blood changes

  • Blood volume increases by 50% while red blood cell volume increases by only 20-30% leading to a dilutional anaemia during pregnancy.

  • Increase in heart rate and output of the heart may lead to the common symptom of palpitations.

  • Blood pressure tends to decrease between 12-24 weeks and start to increase again in the third trimester


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