Autoimmune disorders, including Graves' disease (see Pregnancy Complicated by Disease: Thyroid Disorders During Pregnancy), are more common among women, particularly pregnant women. The abnormal antibodies produced in autoimmune disorders can cross the placenta and cause problems in the fetus. Pregnancy affects different autoimmune disorders in different ways.

Systemic lupus erythematosus (lupus): Lupus may appear for the first time, worsen, or become less severe during pregnancy. How a pregnancy affects the course of lupus cannot be predicted, but the most common time for flare-ups is immediately after delivery.

Women who develop lupus often have a history of repeated miscarriages, fetuses that do not grow as much as expected, and preterm delivery. If women have complications due to lupus (such as kidney damage or high blood pressure), the risk of death for the fetus or newborn is increased.

In pregnant women, lupus antibodies may cross the placenta to the fetus. As a result, the fetus may have a very slow heart rate, anemia, a low platelet count, or a low white blood cell count. However, these antibodies gradually disappear over several weeks after the baby is born, and the problems they cause resolve except for the slow heart rate. Women with lupus may need to take prednisone (a corticosteroid) by mouth while they are pregnant.

Myasthenia gravis: This disorder, which causes muscle weakness, does not usually cause serious or permanent complications during pregnancy. However, women may need to take higher doses of drugs (such as neostigmine) used to treat the disorder or may need to take corticosteroids or drugs that suppress the immune system (immunosuppressants). Very rarely during labor, women who have myasthenia gravis need help with breathing (assisted ventilation).

The antibodies that cause this disorder can cross the placenta. So about one of five babies born to women with myasthenia gravis is born with the disorder. However, the resulting muscle weakness in the baby is usually temporary because the antibodies from the mother gradually disappear and the baby does not produce antibodies of this type.

Immune (idiopathic) thrombocytopenic purpura (ITP): In ITP, antibodies decrease the number of platelets (also called thrombocytes) in the bloodstream. Platelets are cell-like particles that help in the clotting process. Too few platelets (thrombocytopenia) can cause excessive bleeding in pregnant women and their babies. If not treated during pregnancy, the disorder tends to become more severe. Corticosteroids, usually prednisone given by mouth, can increase the number (count) of platelets and thus improve blood clotting in pregnant women with this disorder. However, prednisone increases the risk that the fetus will not grow as much as expected or will be born prematurely.

Women who have a dangerously low platelet count may be given high doses of immune globulin intravenously shortly before delivery. This treatment temporarily increases the platelet count and improves blood clotting. As a result, labor can proceed safely, and women can have a vaginal delivery without uncontrolled bleeding.

Pregnant women are given platelet transfusions only when a cesarean delivery is needed and when the platelet count is so low that severe bleeding may occur.

Rarely, when the platelet count remains dangerously low despite treatment, the spleen, which normally traps and destroys old blood cells and platelets, is removed. The best time for this surgery is during the 2nd trimester.

The antibodies that cause the disorder may cross the placenta to the fetus. However, they rarely affect the platelet count in the fetus.

Rheumatoid arthritis: If arthritis has damaged the hip joints or lower (lumbar) spine, delivery may be difficult for the woman, but this disorder does not affect the fetus. The symptoms of rheumatoid arthritis may lessen during pregnancy, but they usually return to their original level after pregnancy.

Last full review/revision December 2008 by Sean C. Blackwell, MD