Myasthenia gravis in pregnancy: report on 69 cases

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Abstract

Objective: To review our experience with pregnancies in women with myasthenia gravis (MG). Study design: Sixty nine pregnancies among 65 women with MG patients managed by our department over 28 years were included. The course of the disease in pregnancy, mode of delivery and postpartal period were evaluated. Results: One pregnancy miscarried. In 15% of patients the MG deteriorated in pregnancy a further 16% in the puerperium. 17% of pregnancies were delivered by cesarean section, one due to myasthenia exacerbation. All women with puerperal infections developed exacerbations. One neonatal death, not attributable to myasthenia, was recorded. Transitory neonatal myasthenia gravis (TNMG) was diagnosed in 30% infants. Its incidence was inversely associated with maternal disease duration (P<0.05). Newborns of thymectomized mothers showed lower rate of neonatal myasthenia compared to those of non-thymectomized women (P<0.05). Conclusions: MG patients can have normal pregnancy and delivery but the course is unpredictable. Shorter disease history and infection predispose to puerperal exacerbation. Maternal thymectomy lessens the likelihood of neonatal myasthenia. An interdisciplinary approach is required for managing the pregnant women with MG.

Introduction

Myasthenia gravis (MG) is an autoimmune disorder affecting the neuromuscular junction. It may considerably affect the course of the pregnancy and cause serious complications in both the mother and the infant [1]. Fluctuating fatigue and progressive muscular weakness upon repeated movements are prevailing in clinical feature. Antibodies to nicotinic acetylcholine receptors (n-ACh-R) are the cause of the disturbant nerve impulse transmission to muscle fibers. Those antibodies belong to IgG immunoglobulin group. They may cross placenta and cause transitory neonatal myasthenia gravis (TNMG).

MG is relatively frequent among women of reproductive age (1:10,000 down to 1:50,000) so the obstetrician will certainly meet such patients sooner or later. The impact of pregnancy on the MG course is a subject of numerous reports [2], [3], [4]. Generally, in one third of the pregnant women the disease exacerbates, whereas in two third it shows no changes. More or less severe deterioration may develop in the first trimester. MG signs and symptoms in pregnant women tends to improve throughout second and third trimester coinciding with immunosuppression which normally takes place in that period. A complete remission occurs in some patients. The body’s immunological response reactivates again at time of delivery and in puerperium as well. This may be the cause of an exacerbation and deterioration of MG. The outcome of earlier pregnancies does not help in predicting the course of the current pregnancy or the future ones [3] The disease is not associated with sterility, yet a considerably higher incidence of spontaneous abortions does exist in the observed MG patients. No data are available on the increased incidence of premature labors or preeclampsia in pregnant women suffering from MG [5], [6].

TNMG is a transitory form of myasthenia occurring in 12–20% of infants born to myasthenic mothers [7]. The clinical features of TNMG develop in the first 4 days of life: in two thirds of the cases the syndrome develops within a few hours after birth, and in 8% of the cases within the first day of life [8]. The symptoms usually last for 3 weeks. TNMG develops due to placental transfer of the nicotinic acetylcholine receptor antibodies from maternal to fetal blood circulation. A correlation occurs between a drop in antibodies titer and the infant’s muscular strength. The reason for a delayed onset of MG in the infant is an anticholinesterase drug, passing through the placenta, so that neonatal myasthenia is manifested only after the drug is excreted and decomposed in the infant. The TNMG signs are lethargy, slow respiration, faint cry, generalized muscular weakness and absence of Moro’s reflex. The infants show difficulties in sucking and breathing. The diagnosis can be confirmed by 0.05–0.1 ml edrophonium chloride (Tensilon, Roche, Basel, Switzerland) administered subcutaneously. In case of a remission, the diagnosis is confirmed and the infant is to be treated with acetylcholinesterase inhibitors. Appropriately treated, TNMG has the favorable outcome today [9]. It is remarkable that the mother’s disease gravity is not accompanied by the development of TNMG [4].

The purpose of this study is to review our experience with 65 MG patients and course of their 69 pregnancies. We have focused on MG signs and symptoms deterioration, incidence of obstetric interventions during labor, and incidence of transitory TNMG.

Section snippets

Material and methods

From 1972 to 1999, 65 patients with MG and a total of 69 pregnancies were treated and delivered at the Department of Gynecology and Obstetrics, University Hospital Center, Zagreb. The course of pregnancy, labor and puerperium were analyzed retrospectively, as well as the neonatal period in 70 infants born to MG mothers (two pregnancies involved twins, whereas one ended as miscarriage). Data were collected from patients’ medical documentation.

The diagnosis of MG was established at the Department

Results

The average age of the patients was 28.0±4.7 years, (range 21–41 years). Thirty-eight (55%) were para I, 20 (30%) were para II, 10 (14%) were para III, and 1 (1.4%) para IV.

In 36 (52.2%) patients MG lasted less than 5 years, nine of them developed the disease with the onset of pregnancy. In 19 (27.5%) MG lasted between 5 and 10 years, and in 14 (20.3%) over 10 years.

Seven (10.7%) patients had ocular form, 21 (32.3%) had mild, 29 (44.6%) had moderate and eight (12.3%) had severe form of the

Comment

Recent references dealing with present topic mostly consist of reports on single [10] or low-number [11], [12] cases, hence our reliance on earlier reports for a better insight.

In 22 myasthenic pregnant women, with a total of 33 pregnancies, Osserman showed that in one third of the pregnant women an exacerbation occurred, whereas two third showed no change or a remission occurred [2]. The exacerbation usually occurs during the first trimester, with minor changes during the second and third

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