Pregnancy and Myasthenia Gravis

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Myasthenia gravis typically affects females during their reproductive years. Difficulties specific to pregnant patients can be concerning, and the course of myasthenia gravis during pregnancy is hard to predict. Patients may have disease exacerbation, crisis, or, interestingly enough, remission. Although the disease course is variable, pregnant patients face risks of exacerbation, respiratory failure, adverse drug response, crisis, and death.
In a large study, exacerbations occurred in approximately 41% of patients during pregnancy and in 29.8% of patients postpartum. Approximately 4% of patients died because of worsening of the disease or because of treatment complications.

Complications

Some rare problems may occur during pregnancy. In 2000, Ellison and colleagues reported a rare case of bone marrow suppression in a patient who experienced leukopenia and thrombocytopenia during all 3 of her pregnancies. The patient improved after receiving 65 mg of human immunoglobulin (1 mg/kg for 2 d). Labor was induced, and she delivered a boy. Interestingly, 1 day after each delivery, her platelet and white blood cell (WBC) counts increased. On the third postnatal day, her platelet count increased to 128 X 109/L from 82 X 109/L after immunoglobulin transfusion, and her WBC count increased to 2.5 X 109/L from 2.2 X 109/L.
Some exacerbations can be linked to the anxiety and physiologic stress of pregnancy. Hypoventilation is a risk during pregnancy, because respiratory muscles are weakened from myasthenia gravis. Also, the lungs do not become fully inflated, because the diaphragm is elevated during pregnancy. Approximately 20% of patients experience respiratory crises that require mechanical ventilation. This is one of most severe complications.
Infections due to decreased immunity play a very important role in the exacerbation of myasthenia gravis during pregnancy.
Labor may be complicated. Although smooth muscle is not affected by autoantibodies and the uterus is not compromised, the second stage of labor involves striated muscle. The patient may become exhausted during labor and may require assistance. Operative vaginal delivery has been recommended.

Preeclampsia

In 1979, Duff described an association between myasthenia gravis and preeclampsia. He observed preeclampsia in 3 patients and reasoned that altered immune status could be an etiologic factor in preeclampsia. Preeclampsia may also be problematic from a pharmacologic standpoint, because magnesium sulfate is contraindicated in myasthenic patients. In the event that eclampsia does present in the pregnant patient with myasthenia gravis, phenytoin is the currently accepted method of treatment.

Neonatal impact

Not only is the mother at risk, her baby also faces significant risks, including neonatal myasthenia gravis, prematurity, severe malformation, and death.
Rates of neonatal myasthenia gravis are as high as 10-20%. Affected babies show respiratory distress and inadequate suck. Babies are affected by transient myasthenia, which is self-limited and lasts approximately 3 weeks. This is due to the transplacental transfer of antibodies. This is puzzling because no close correlation exists between maternal disease severity and neonatal myasthenia, and no correlation exists between the occurrence of neonatal myasthenia gravis and maternal anti-AChR antibody titers.
More severe neonatal problems have been reported, including death from malformations attributable to myasthenia gravis. Carr and colleagues reported that the most common fetal abnormalities are pulmonary hypoplasia and arthrogryposis.Prematurity is also a concern. Breastfeeding by the mother with myasthenia gravis is safe if she is following a treatment course that utilizes pyridostigmine or corticosteroids; however, mothers with myasthenia gravis being treated with azathioprine, methotrexate, mycophenolate mofetil, or cyclophosphamide, as well as mothers of newborns with myasthenia gravis, should not breastfeed.