The incidence of intrauterine fetal death in type 1 diabetic patients is significantly higher than in the general population (1). Although vascular disease, poor glycemic control, polyhydramnios, fetal macrosomia, and preeclampsia are associated with a higher incidence of fetal death, the etiology of the increased stillbirth rate remains unknown. Besides other complications, infants of diabetic mothers have long been recognized to be at risk of having hypertrophic cardiomyopathy, a condition that is characterized by thickening of the interventricular septum and ventricular walls, and by systolic and diastolic dysfunction of the neonatal heart. This condition is normally asymptomatic in utero and may only result in congestive heart failure in the immediate postnatal period, although this is uncommon and transient (2).

A 30-year-old woman, gravida 3, para 0, abortus 2, was referred to our unit for the assessment of suspected fetal macrosomia at 35 weeks of gestation. She had been diagnosed with type 1 diabetes at age 13 years. In the current pregnancy, her glycemic control had been suboptimal, as confirmed by an HbA_1c (A1C) value of 7.6% obtained at 31 weeks. The ultrasound scan performed in our unit showed fetal abdominal growth above the 95th percentile. There was associated polyhydramnios, and the fetal heart showed features of hypertrophic cardiomyopathy. The umbilical artery showed an abnormal pattern of flow. There were no signs of fetal hydrops, but the fetus showed reduced movements. In view of these findings, reevaluation of the fetus was planned in 4–6 h to decide further management.

Within a few hours, the patient started complaining of uterine contractions. An external fetal monitor was applied, showing a fetal heart baseline rate of 160 bpm, with reduced variability and repetitive late decelerations, indicating an ominous outcome if untreated. An emergency Caesarean section was performed, delivering a female infant of 3,575 g (weight above 95th percentile for gestation) with an Apgar score of 4, 7, and 10 at 1′, 5′, and 10′, respectively. No signs of abruption were noted clinically or at pathological examination of the placenta. The newborn needed nasal continuous positive air pressure for the first 12 h for stabilization. Postnatal echocardiography confirmed the diagnosis of hypertrophic cardiomyopathy. Treatment with propranolol was started, and the neonate was discharged on day 7. A follow-up visit at 3 months after delivery showed resolution of the cardiac hypertrophy.

One previous report has described a case of stillbirth at 37 weeks of gestation associated with previously undiagnosed hydrops fetalis and hypertrophic cardiomyopathy in the fetus of a diabetic mother (3). The same authors suggested that unexplained fetal deaths described in earlier reports (4–6) might be attributable to hypertrophic cardiomyopathy. In the present case, the fetus showed no signs of hydrops or cardiac failure, but the abnormal umbilical flow suggested a frail state near to decompensation. The increased cardiac work requirement brought on by the onset of uterine contractions was sufficient to induce acute fetal distress, as documented by a grossly abnormal fetal heart rate pattern. These findings indicate that diabetic hypertrophic cardiomyopathy can present with acute fetal distress even in absence of hydrops and suggest that this condition might be one of the causes of the increased stillbirth rate in pregnancies complicated by type 1 diabetes.