Maternal Adaptations to Pregnancy

A woman's body responds to pregnancy by making a series of profound structural and physiological changes. She burns an additional ∼400 kcal/day at rest and increases her oxygen consumption by ∼33% compared to her nonpregnant state. The average weight gain of a woman is ∼12 kg over the course of pregnancy. Maternal blood volume increases by 30–50% during pregnancy, and the heart chambers enlarge allowing a larger stroke volume. Together with the increased heart rate and decreased vascular resistance to flow, cardiac output often increases by ∼50%. Women who are pregnant hyperventilate and increasingly drive their arterial carbon dioxide tensions down, resulting in a mild compensated respiratory alkalosis. Women retain water during pregnancy, and associated renal changes are dramatic. Effective renal plasma flow and glomerular filtration rate increase over the course of gestation as renal vascular resistance is decreased. The molecular mechanisms underlying these changes have been little studied.