Congenital malformations in diabetic pregnancies. Clinical viewpoints.

A consecutive series of 2,587 newborn infants of diabetic mothers treated during pregnancy and delivery in the period 1926 to 1983 has been analysed. The malformation rate was 6.6%. The series has been divided into five consecutive periods each comprising around 500 infants. During the first four periods the frequency of congenital malformations (CM) was remarkably constant also when related to the severity of the maternal diabetes. During the latest period from 1979 to 1983 a significant decrease in the frequency and severity of CM in infants of diabetic mothers was seen, most marked in the group with more severe maternal diabetes (White's classes D + F). One hundred and thirty-five insulin-dependent diabetic women with regular menstrual histories were examined by ultrasonic scanning in the 7th to 14th week of pregnancy. As judged by the crown-rump length 53 fetuses were smaller than normal. The term early growth delay is used for this phenomenon. Nine of the 135 fetuses had major CM and seven of them were smaller than normal in early pregnancy. These observations show that fetuses that are significantly smaller than normal in early pregnancy carry a higher risk of being malformed and suggest a common mechanism behind early growth delay and induction of abnormal embryogenesis.