How is myasthenia gravis (MG) treated during pregnancy?

Updated: Aug 20, 2019
  • Author: Carmel Armon, MD, MSc, MHS; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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Autoimmune myasthenia gravis (MG) is an uncommon disease of the neuromuscular junction characterized by striated muscle fatigue and weakness. MG frequently affects young women of childbearing age (20-40 years of age), and pregnancy creates potential risks for both the mother and the fetus. [62, 63] (See Myasthenia Gravis and Pregnancy.) During pregnancy, the course of disease is unpredictable. In a series of 69 pregnancies in 65 women with MG who were treated in a single obstetrics department, 15% had deterioration during pregnancy, and 16% had deterioration during the puerperium. [64] In a report of 64 pregnancies in 47 women with MG, 39% of those treated improved, 42% were unchanged, 19% had deterioration, and 17% of those not receiving therapy had deterioration. [64] Myasthenic symptoms of 28% of women worsened after pregnancy. Therefore, successful management necessarily involves recognizing the potential for myasthenic crisis, optimizing anticholinesterase or immunosuppressivemedicationtreatment, and preparing for the possibility of transient neonatal MG. The challenging care of a woman with MG who is contemplating pregnancy should begin with careful planning and the collaboration of obstetricians and neonatal intensive care specialists. Counseling should address current knowledge, risks, and available treatments. Women with MG who decide to become pregnant should receive prenatal care from providers with experience in treating this disease, and delivery should be performed at a hospital that can manage any complications that may arise. [62, 65, 66, 67] Management of pregnancy and delivery The risks and benefits of continuing medication or other immunosuppressive therapy should be discussed, and counseling should begin when the pregnancy is planned. Treatment of MG should be optimized, and clinical improvement should be maximized. The need for immunosuppressant treatment depends on the severity of illness and should be modified according to the duration andseverity of thepatient’s symptoms of MG. If possible, physicians with experience in treating patients with this disease should perform the delivery at a hospital with the capability to treat both women and infants with complications of MG. In the 1967-2000 Medical Birth Registry of Norway, a population-based cohort study, the potential for cesarean delivery doubled in 127 births by 79 mothers with MG (17.6%) as compared with a reference group (8.6%). [65] The number of births requiring medication to induce labor was not increased. Serious birth defects occurred in 5 children of mothers with MG, but the rate of such defects was not significantly greater than that of a reference group. Preterm rupture of the amniotic membranes was the only complication that occurred more frequently in the MG group than in a comparison group. [65] Rates of neonatal mortality, birth weight, or prematurity did not differ. Pregnancy did not worsen the long-term outcome of MG. [68] Cesarean delivery is recommended ifit isnecessary for obstetric reasons, and regional anesthesia is safe with correct drug selection. [66] To reduce the potential for adverse effects on the fetus, immunosuppressive medication should be discontinued if possible, or the dose should be minimized. However, little information about this topic is available in the literature. Some information can be derived from the treatment of patients with other autoimmune disorders, but separating the effects from the potential risks of the treated illness is difficult.

Prednisone or prednisolone is associated with a slightly (< 1%) increased risk of cleft palate. High-dose corticosteroids may be associated with premature rupture of amniotic membranes. [66] Methotrexate may be associated with fetal malformations and thus is not recommended for use during childbearing years. [65] Although women taking azathioprine have generally been advised against pregnancy, no teratogenicity or specific malformation pattern has been definitively demonstrated with therapeutic doses in humans. [65, 66]

In a retrospective review of pregnancy outcomes, infants exposed to azathioprine were at risk for the development of reversible leukopenia, anemia, thrombocytopenia, reduced immunoglobulin levels, infection, or thymic atrophy. [65, 66] Babies born to mothers treated with azathioprine have an increased risk of myelosuppression and immunosuppression. [66]

Cyclosporine increases the risk of low birth weight, prematurity, and spontaneous abortions. [65, 66] Nausea and vomiting early in pregnancy may interfere with pyridostigmine dosing. Drug schedules may have to be altered because of increased renal clearance, expanded blood volume, and erratic gastrointestinal absorption. [69]

Discontinuance of maternal immunosuppressants can either worsen or improve MG. If needed, plasma exchange or human intravenous immunoglobulin (IVIg) therapy may be effective and can be safely administered during pregnancy. In theory, plasma exchange can induce premature delivery through large hormonal shifts. [65]

Although MG does not directly affect the uterine smooth muscle, the striated abdominal muscles that contract with the effort of delivery during the second stage of labor may fatigue and weaken more easily than they would if the disease were not present.

Acetylcholinesterase drugs should probably be given parenterally because of their unpredictable oral absorption. Neuromuscular blockers may exaggerate and prolong muscular weakness and should be avoided if possible. Epidural anesthesia is considered relatively safe for vaginal and cesarean deliveries.

Magnesium sulfate is used to prevent seizures in patients with preeclampsia, to treat eclampsia, and to prevent preterm birth in patients with preterm labor; this drug can precipitate weakness by interfering with neuromuscular transmission. Maternal deaths are reported with its use to treat MG in women with preeclampsia. [66]

Consultation with an anesthesiologist should be considered for all pregnant patients with MG.

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