By far the most significant physiologic changes of pregnancy are endocrinologic. Significant increases in production and serum levels of growth hormone, prolactin, thyroxin, parathyroid hormone, calcitonin, and progesterone occur in support of fetal development and parturition.

In addition, pregnancy is associated with positive nitrogen balance and postprandial hyperglycemia and hyperinsulinemia. This latter response is consistent with a pregnancy-induced state of peripheral resistance to insulin, the purpose of which is to ensure sustained supply of glucose to the fetus. Furthermore, the concentrations of plasma lipids, lipoproteins, and lipopolysaccharides increase appreciably during pregnancy and lead to central fat deposition to supply fetal demands.

Blood volume at or near term is approximately 40% above that in nonpregnancy. This hypervolemia of pregnancy meets the demands of pregnancy and protects the mother against impaired venous return and the blood loss of child birth.