Myotonic dystrophy in pregnancy. Prenatal, neonatal and maternal considerations.

Five pregnancies occurred in three women with myotonic dystrophy. Four of the five infants had generalized hypotonia, respiratory failure, swallowing difficulties and arthrogryposis; two of the affected infants died despite intensive treatment. The surviving affected children had a gradual improvement in respiratory and swallowing symptoms but have remained hypotonic and developmentally delayed. The fifth infant was entirely normal. Polyhydramnios was the most constant feature of the affected pregnancies. Three of the four affected fetuses weighed less than 2,500 gm. Other obstetric complications were not prominent. Second-trimester amniocentesis and linkage studies have a role in predicting myotonic dystrophy. Real-time ultrasound can be used in the prenatal diagnosis of neonatal myotonic dystrophy.