Myasthenia Gravis and Pregnancy

Posted On: January 27, 2017 By Nathan D. Fox, MD

Myasthenia gravis (MG) is an autoimmune disorder caused by autoantibodies directed against nicotininc acetylcholine receptors in the skeletal muscle. This condition carries symptoms including muscle weakness in the eyes, limbs, and respiratory muscles. These symptoms usually present after repetitive use, like at the end of the day.

For some patients, MG is only present in the eye muscles, called ocular MG. Not all patients with MG have detectable antibodies, bringing the terms “seropositive” and “seronegative” MG into the medical diagnosis. Ten to fifteen percent of patients with MG have an underlying thymoma, or a tumor originating from cells of the thymus.

Effect of Pregnancy on Myasthenia Gravis

Approximately one-third of patients with MG improve, one-third worsen, and one-third stay the same during pregnancy. However, in the first few months after delivery, there is a high-rate of increased severity of symptoms, which is common with all autoimmune conditions.

Effect of Myasthenia Gravis on Pregnancy

There is no strong evidence that MG significantly worsens pregnancy outcomes, such as preterm birth or fetal growth restriction. However, there is a risk of fetal/neonatal neuromuscular involvement due to the maternal antibodies crossing the placenta and entering the fetal circulation. This risk requires close fetal and neonatal assessment.

Abnormal fetal findings may include polyhydramnios (high amniotic fluid), due to impaired fetal swallowing) and decreased fetal movement and breathing. In severe cases, fetal arthrogryposis may develop, which is characterized by joint contractures and even pulmonary hypoplasia (incomplete development of the lungs). Therefore, serial assessment by ultrasound is recommended.

After birth, transient neonatal MG develops in approximately 10 to 20 percent of babies born to women with MG. This risk does not appear to correlate with maternal antibodies nor the duration of the disease. Symptoms usually are present within 48 hours of birth, newborns of women with MG need to be watched closely in the first few days of life for signs of neonatal MG. For women with a prior child affected by neonatal MG, the risk of it developing in following children is higher than 75 percent.

Treatment of Myasthenia Gravis

Treatment of MG is similar to non-pregnant patients, including treatment with acetylcholinesterase inhibitors. If necessary, steroids and other immune modulators can be used. Patients with MG should stay in contact with their treating neurologist, and should undergo cardiac evaluation due to the possible risk of heart disease. Thyroid function should also be examined due to the high coincidence of MG and thyroid disease.

All infections should be treated promptly, and respiratory symptoms should be evaluated thoroughly. The patient should try to avoid physical and emotional stress, when at all possible. Intravenous magnesium, which is sometimes used in pregnancy for certain complications, is contraindicated in pregnancy due to the risk of it precipitating a severe MG crisis. Beta blockers and calcium channel blockers should be avoided as well.

For more information regarding Myasthenia Gravis and Pregnancy or any other question, visit our blog.  For any other concerns, contact Carnegie Imaging.

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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