Background Women with pre-gestational diabetes (PGDM) are at increased risk of pregnancy affected by a congenital anomaly. National guidance recommends enhanced antenatal ultrasound screening for cardiovascular defects.

Aim To compare antenatal detection of congenital anomaly, and outcomes of affected pregnancies, in women with and without PGDM.

Methods We linked data for 1996–2008 from the Northern Diabetes in Pregnancy and Northern Congenital Abnormality Surveys in the North of England. Antenatal detection of major structural congenital anomaly in singleton pregnancies resulting in spontaneous abortions ≥20 weeks, terminations of pregnancy for congenital anomaly, stillbirths and live births was compared between women with and without PGDM.

Results There were 120 affected offspring among 1677 pregnancies in women with PGDM (71.6 per 1000), compared to 19.1 per 1000 in women without diabetes (RR 3.8, 95% CI 3.2 to 4.5). 44 (37%) anomalies in women with PGDM were cardiovascular anomalies, but the risk was increased for all major groups. 51% of all anomalies were detected antenatally in women with PGDM compared with 41% in those without (RR 1.23, 95% CI 1.03 to 1.47). For cardiovascular anomalies, 32% versus 10% were detected antenatally (RR 3.06, 95% CI 1.96 to 4.77). Outcome of affected pregnancy was similar in women with and without PGDM: 18% versus 14% resulted in termination of pregnancy and 72% versus 78% were alive at 1 year. 3% of cardiovascular anomalies resulted in termination; none in women with PGDM.

Conclusion A higher proportion of anomalies was detected antenatally in women with PGDM, but this did not influence pregnancy outcomes.