Two infants with congenital myotonic dystrophy complicated by pleural effusions and hydrops fetalis are reported from the Valley Children’s Hospital, Fresno, CA, and the Royal Alexandra Hospitals, University of Alberta, Edmonton, Alberta, Canada. The mothers had myotonic dystrophy diagnosed at or after the delivery. The pregnancies were complicated by polyhydramnios, and the infants were delivered by cesarean section because of breech presentation. Infant 1 was areflexic, profoundly hypotonic, failed to breathe spontaneously, and died at 3 days of age. Muscle biopsy at autopsy revealed extreme muscle immaturity with poor type I/II fiber differentiation, type I and type lie fibers, and central nucleation. Infant 2 died 25 min after delivery despite aggressive resuscitation. The authors cite 6 other cases of congenital myotonic dystrophy with fetal hydrops and 2 with pleural effusions. Fetal hydrops may obscure the diagnosis, especially if the mother is asymptomatic. 
COMMENT. Chromosomal defects, cardiac abnormalities, and genetic syndromes are described with fetal hydrops but congenital myotonic dystrophy has been associated infrequently. When a mother is known to have myotonic dystrophy, the fetus should be monitored for abnormal breathing patterns and pleural effusions. A hypotonic infant born with pleural effusion or hydrops should alert the examiner to check for myotonia in the mother. (See Ped Neur Briefs Sept 1987;1 :29-30).