Risk factors for pregnancy-related clinical outcome in myasthenia gravis: a systemic review and meta-analysis

Objective Myasthenia gravis (MG) is an autoimmune disorder that frequently affects females at reproductive age. Herein, we aimed to assess the associations of clinical factors with pregnancy-related outcome in MG. Methods We searched PubMed and EMBASE for case-control and cohort studies that reported the MG status during or after pregnancy and relevant clinical variables. The data was extracted in proportions and odds ratios (ORs) with 95% confidence intervals (CIs) in subsequent meta-analysis. Results Fifteen eligible articles reporting on 734 pregnancies with 193 worsening and 51 improved episodes were included out of 1765 records. The estimated worsening proportions in total, antepartum and postpartum periods were 0.36 (95% CI 0.25-0.40), 0.23 (95% CI 0.14-0.34) and 0.11 (95% CI 0.04-0.22) respectively. The proportion of pregnancy-related improvement in enrolled patients was 0.28 (95% CI 0.17-0.40), with 0.07 (95% CI 0.00-0.28) during pregnancy and 0.14 (95% CI 0.02-0.34) after pregnancy. No significant associations were disclosed between the clinical factors and MG worsening. Thymectomy before delivery is a strong predictor for MG improvement in postpartum period (OR 4.85, 95% CI 1.88-12.50, p = 0.001). Conclusion The total proportion of pregnancy-related MG worsening and improvement in MG was 0.36 (95% CI 0.25-0.40) and 0.28 (95% CI 0.17-0.40), respectively. Thymectomy before the delivery may aid in clinical improvements associated with pregnancy. Future prospective cohort studies are required to determine more relevant factors.