Congenital malformations among infants whose mothers had gestational diabetes or preexisting diabetes.

BACKGROUND: Diabetes type 1 is associated with an increased risk for infant congenital malformations. It is debated whether this is true also at gestational diabetes.

AIMS: To study occurrence of congenital malformations in infants whose mothers had preexisting or gestational diabetes.

STUDY DESIGN: A register study covering over 1.2 million Swedish births in 1987-1997 based on the Swedish health registries.

SUBJECTS: We identified from the Medical Birth Registry 3864 infants born of women with preexisting diabetes and 8688 infants born of women with gestational diabetes.

OUTCOMES MEASURES: Congenital malformations identified in the Medical Birth Registry, the Registry of Congenital Malformations, and the Hospital Discharge Registry. The rates of congenital malformations among these infants was compared with the population rates.

RESULTS: At preexisting diabetes, the total malformation rate was 9.5% while the rate at gestational diabetes was similar to the population rate, 5.7%. At preexisting diabetes, certain conditions were more common than expected: orofacial clefts, cardiovascular defects, oesophageal/intestinal atresia, hypospadias, limb reduction defects, spine malformations, and polydactyly. For some of these conditions, an excess was found also for infants whose mothers had gestational diabetes. Infants with multiple malformations were in excess at preexisting diabetes but not at gestational diabetes but the specific type of malformations involved were similar in the two diabetes groups.

CONCLUSIONS: It is suggested that in the group of gestational diabetes exists a subgroup with an increased risk for a diabetes embryopathy, perhaps due to preexisting but undetected diabetes type 2.