Course and treatment of myasthenia gravis during pregnancy.

OBJECTIVE: To evaluate the influence of myasthenia gravis (MG) on pregnancy and potential treatment risks for infants and mothers.

BACKGROUND: MG frequently affects young women in the second and third decades of life, overlapping with the childbearing years. Knowledge of the potential effects of 1) pregnancy on the course of MG and 2) the use of immunosuppressive drugs during pregnancy is limited, rendering decision-making difficult for both patient and physician.

METHODS: We studied 47 women who became pregnant after the onset of MG. Immunosuppressive drugs were administered when MG symptoms were not controlled with anticholinesterases. Sixty-four pregnancies resulted in 55 children and 10 abortions.

RESULTS: During pregnancy, MG relapsed in 4 of 23 (17%) asymptomatic patients who were not on therapy before conception; in patients taking therapy, MG symptoms improved in 12 of 31 pregnancies (39%), remained unchanged in 13 (42%), and deteriorated in 6 (19%). MG symptoms worsened after delivery in 15 of 54 (28%) pregnancies. Anti-acetylcholine receptor antibody (anti-AChR ab) was positive in 40 of 47 mothers and was assayed in 30 of 55 newborns; 13 were positive and 5 of 55 (9%) showed signs of neonatal MG (NMG). All affected babies were seropositive.

CONCLUSIONS: Pregnancy does not worsen the long-term outcome of MG. The course of the disease is highly variable and unpredictable during gestation and can change in subsequent pregnancies. The occurrence of NMG does not correlate with either maternal disease severity or anti-AChR antibody titer. Immunosuppressive therapy, plasmapheresis, and i.v. human immunoglobulins can be administered safely if needed.