Clinical characteristics and outcome of pregnant patients with myasthenia gravis

Objective: To study the clinical characteristics of pregnant patients with myasthenia gravis (MG) and the influence of MG to pregnancy. Methods: A retrospective study was conducted including 28 MG patients with 38 pregnancies admitted to the 8th Medical Center of PLA General Hospital between January 2013 and October 2018. Data were collected including clinical scores of MG, serum level of acetylcholine receptor (AChR) antibodies, abnormal repetitive nerve stimulation (RNS) and history of thymectomy before pregnancy. The course of pregnancy, delivery and neonatal outcome were also analyzed. According the outcome of MG, patients were divided into three groups, i.e. improvement group, stable group and deterioration group. Results: (1) The age of MG patients ranged from 21 to 36 (27±4) years. The previous course of MG was 0.5-17.2 (7.4±5.8)years. Based on Osserman clinical type, type ⅡA was the most common one [44.1% (15/34)], followed with type Ⅰ [29.4% (10/34)], type ⅡB [23.5% (8/34)] and type Ⅳ (2.9%).(2)There were 38 pregnancies in 28 women whose pregnancy outcomes resulted in one spontaneous abortion, three embryonic arrest and 34 live births. All abortions developed in the first trimester. Among the 34 pregnancies with live births, the symptoms of MG improved in 16 pregnancies (47.1%), whereas those deteriorated in 10 pregnancies (29.4%) during the first or third trimester and remained stable in 8 pregnancies (23.5%). (3) Compared with improvement group and stable group, the deterioration group had shorter duration of MG [(1.1±0.5) years vs. (7.1±5.1) years, (9.0±5.4) years respectively], higher clinical scores (20.9±6.0 vs. 14.8±6.6,13.3±5.0) and more frequent abnormal RNS(9/10 vs. 8/16, 4/8) and type ⅡB(6/10 vs. 1/16, 1/8) before pregnancy. Positive rate of serum AChR antibody and percentage of thymectomy before pregnancy were comparable between three groups. (4) Spinal anesthesia was performed in 23 pregnancies and 11 cases were vaginal delivery. No transient neonatal MG were found in live-born infants. Conclusions: Pregnancy in patients with under-controlled myasthenia gravis should not be discouraged. The outcome of MG is affected by the duration of MG, MG score and RNS before pregnancy. The first and third trimesters of pregnancy are considered high-risk periods for MG exacerbations. Neonatal transient myasthenia is uncommon, but the newborn should be carefully monitored by obstetricians and neurologists.