To review the interaction between myasthenia gravis (MG) and pregnancy. 

The course of MG during pregnancy and delivery is variable, with reports of up to 30% patients experiencing worsening MG, and a prevalence of transient neonatal myasthenia of 12-20%. Patient education, frequent monitoring, referral to high risk pregnancy clinics and access to neonatal care are recommended. We reviewed our experience with MG and pregnancy when using these recommendations. 

We performed a retrospective chart review of patients with confirmed MG who had a pregnancy between 2001 and 2019.

We identified 28 pregnancies in 20 patients. All patients had generalized MG. Of 13 tested patients, 10 (77% ) had elevated acetylcholine receptor antibodies and one (8%) had anti-MuSK antibodies, 15% were seronegative. The mean age at first pregnancy was 29.7 ± 5.7 years and the mean MG duration was 5.7 ± 5.9 years. Two patients had onset of MG during pregnancy and 1 following delivery. Worsening was observed in 16 (57%) pregnancies: seven during pregnancy and 9 following delivery.Of 7 patients who worsened during pregnancy, 5 had MG for less than 2 years, 1 for 3 years and 1 for 9 years. Three patients stopped immunosuppressive treatment during pregnancy, all worsened. Myasthenic crises occurred in 4 (14%), pregnancies, including one patient with newly diagnosed MG and one who stopped immunosuppressive medications. Caesarian section occurred in 29% of pregnancies. The rate of delivery complications was 7%, of premature births 7% and of neonatal MG 7%.

We found a lower rate of neonatal MG than previously reported. The risk of Caesarean delivery was similar to the general population.  A high proportion of patients worsened during pregnancy, especially in patients with MG for less than 2 years. Stopping immunosuppressive treatments during pregnancy was associated with worsening MG symptoms.