Immunologic adaptations during pregnancy.

Many complementary changes occur in a pregnant woman's immune system to protect the fetus from attack while maintaining maternal defenses against disease. Enhancements occur in immune elements that fight bacterial infections. Conversely, suppression of T-cell activity causes increased susceptibility to viral infections, such as hepatitis, rubella, herpes, and human papilloma virus, and leads to an irreversible reduction in helper T cells in women infected with the human immunodeficiency virus. Local secretion of corticosteroids and changes in cytokine concentration in the reproductive tract protect the fetus from rejection. Understanding these changes assists the perinatal nurse in assessing and counseling women of childbearing age.