Adaptations to pregnancy

Pregnancy is associated with dramatic changes in the structure and function of the mother’s body. A woman’s appetite is increased during pregnancy and is even higher if she carries a boy baby. It is important for a woman to eat a nutritious diet before and during pregnancy to ensure adequate nutrient delivery to the growing fetus. While excess weight gain has detrimental consequences for the baby, the optimal weight gain recommended by experts depends on the maternal body mass index at the time of pregnancy. The metabolic rate is increased during pregnancy as the amount of oxygen consumed by the heart, the kidney, the breast, and the pregnant uterus is increased. To meet the oxygen demands of these organs and others, cardiac output is increased as both stroke volume and heart rate go up. The arterial tree is more compliant during pregnancy and the resistance to blood flow is decreased. A pregnant woman also carries more oxygen in her blood in spite of a lower concentration of red blood cells (hematocrit), because the rate and depth of ventilation is increased which leads to higher oxygen concentrations in the lungs and arterial blood. A woman’s blood volume is increased early and throughout pregnancy even as the hematocrit decreases. The combination of changes in cardiovascular systems and the respiratory systems delivers more oxygen to the uterus, placenta and fetus. Renal blood flow is increased as the kidney performs more work and uses more fuel. Exercise during pregnancy promotes the health of both mother and baby.