Obstetric and Neonatal Outcomes in Patients With Maternal Myasthenia Gravis: A Nationwide Cohort Study

Muscle weakness, autoantibodies, and medication use in myasthenia gravis (MG) can complicate pregnancy and delivery. Vaginal delivery is encouraged despite increased risk of acute operative delivery. Our aim was to assess childbirth outcomes related to MG in a current, unselected, nationwide birth cohort.

This cohort study included all singleton births in the Medical Birth Registry of Norway from 1999 to 2022. Maternal MG, defined as MG diagnosis or pyridostigmine use, was identified from current and previous pregnancies. We compared adverse pregnancy, delivery, and neonatal outcomes between MG and non-MG births, with mode of delivery as the main outcome. Odds ratios (ORs) with 95% CIs, adjusted for year of birth, maternal age, parity, civil status, and autoimmune comorbidities, were estimated with logistic regression. In subanalyses, we investigated cesarean section (C-section) rates within Robson-10 subgroups and C-section indications.

There were 134 MG births and 1,351,032 non-MG births. Elective C-section was twice as likely if the mother had MG (adjusted OR [aOR] 1.8, 95% CI 1.1-3.1), but emergency C-section and operative vaginal delivery were not more common. MG increased the risk of induction (aOR 1.5, 1.0-2.3), neuraxial anesthesia (aOR 1.5, 1.1-2.1), episiotomy (aOR 1.8, 1.1-3.0), preterm prelabor rupture of membranes (aOR 2.7, 1.1-6.6), prolonged hospitalization after delivery (aOR 1.8, 1.3-2.7), low birthweight (aOR 2.4, 1.3-4.4), feeding problems (aOR 4.9, 2.5-9.5), and transfer to a neonatal unit (aOR 5.1, 3.6-7.2). Transient neonatal MG (TNMG) was diagnosed in 5 of 134 children (4%). In subanalyses, the crude C-section rate was increased in preterm MG births (50% in MG vs 19% in non-MG) and in MG births after previous C-section (75% in MG vs 47% in non-MG).

In this registry-based study, the higher rate of elective interventions suggests a proactive management of MG deliveries. The lower C-section threshold for MG births with relative obstetric indications may be justified, but most vaginal deliveries were uncomplicated. Adverse outcomes were generally not increased in the MG group compared with the general population, although episiotomy and prolonged hospitalizations were more frequent. Notably, 40% of MG-exposed infants had feeding difficulties and hypotonia or required neonatal care, suggesting underdiagnosis of TNMG.