Detection of fetal structural malformations by ultrasound in insulin-dependent pregnant women.

A total of 136 insulin-dependent pregnancies was referred to our ultrasound unit for an anomaly scan. In 94 cases the scan was requested between 17 and 22 weeks of gestation (median 20 weeks), in the remaining 42 cases the patient was not referred until after 24 weeks (median 27 weeks), which is too late for termination of pregnancy to be exercised. From the available data, optimal metabolic control was attempted in at least 80% of cases between 4-8 weeks after conception. The incidence of structural anomalies was 8.1%, the majority comprising cardiac and central nervous system malformations. Prenatal ultrasound detection of fetal structural defects was only feasible in seven (64%) out of 11 affected pregnancies. The missed structural anomalies were of cardiac origin in three cases and of gastrointestinal origin in the remaining case. Maternal obesity was present in 72% of our patients and was responsible for false negative results in three out of four cases with a fetal structural defect. This diagnostic limitation should be discussed with the parents when counselling takes place. The high incidence of structural defects (8.1%) and subsequent high perinatal mortality rate (64%) emphasizes the importance of preconceptional metabolic control in insulin-dependent diabetic women.