Physiologic adaptations of pregnancy.

Normal pregnancy changes include physiologic anemia, leukocytosis, and thrombocytopenia. Cardiac rate and stroke volume increase, vascular resistance falls, and creatinine clearance markedly rises. Thyroid binding globulin and cortisol binding globulin both increase, as do complement proteins and fibrinogen, the latter resulting in a normally high erythrocyte sedimentation rate. Estrogen and progesterone rise dramatically. Low back pain, hip and sacroiliac complaints are common. The cytolytic activity of natural killer (NK) cells is decreased, as are adhesion and chemotaxis of phagocytic cells. Antibody responses are normal. CD4 cells proportionately decrease. A large number of circulating proteins suppression lymphocyte proliferation, and T-cell interleukin-2 (IL-2) production may be suppressed. In studies of pregnant patients, controls must include normal pregnant women.