Risk of congenital anomalies detected during antenatal serum screening in women with pregestational diabetes

BACKGROUND: Most studies comparing women with and without pregestational diabetes mellitus have not systematically screened for fetal anomalies in early pregnancy, potentially leading to selection bias. AIM: To evaluate the risk for certain congenital anomalies in women participating in an antenatal maternal screening program. DESIGN: Retrospective cohort study. METHODS: We studied all women who underwent antenatal maternal serum screening in Ontario from 1994 to 2000. Fetal anomalies were documented antenatally by ultrasonography or at autopsy, and postnatally diagnosed birth defects were recorded after 20 weeks gestational age for all live- and stillborn affected infants. We compared the risk of open neural tube defects and urinary tract defects among women with and without pregestational diabetes. RESULTS: Of 413,219 women screened during pregnancy, 2069 (0.5%) had diabetes. Compared to non-diabetic women, the adjusted odds ratios (95%CI) for neural tube and urinary tract defects among women with diabetes were 2.5 (0.9-6.8) and 2.6 (1.4-4.9), respectively. DISCUSSION: Among women who undergo second trimester maternal serum screening, pregestational diabetes is associated with an increased risk of having a fetus with an open neural tube defect or urinary tract disorder.