Aim To categorise and investigate the effect of maternal ethnicity on major fetal congenital anomalies (CA) in mothers with type 1 and 2 diabetes from the West Midlands Diabetes in Pregnancy Cohort Study 2002–2003.

Methods Demographic, antenatal and outcome data for pregnancies registered in West Midlands region between 1 March 2002 and 28 February 2003 was obtained. The data regarding pregnancies resulting in a major fetal CA (ICD10 classification) were cross-checked with regional CA registry data, postmortem reports and postnatal paediatric examinations.

Result There were 32 major CAs in the cohort (426 babies; 370 registerable births). The congenital malformation rate (CMR) is 82.1/1000 births in the WM. There was no difference in the CMR for type 1 or type 2 maternal disease. 63% of these pregnancies resulted in a baby alive at 28 days. 78% of CAs occured in the European group, with the highest CMR being found in European mothers with type 2 diabetes (109/1000 total pregnancies). 13% of CAs occured in the South-Asian population and 6% only to Afrocaribbean mothers. The main categories of anomalies diagnosed were cardiac (37%), central nervous system (19%) and limb/musculoskeletal (16%). The antenatal detection rate by ultrasound for all cases and for cardiac cases only was 55–60%.

Conclusion In the WM the CMR is four times higher than the non-diabetic maternal population. Maternal ethnicity has a major influence on prevalence rates. Detailed ultrasound assessment, especially of the fetal heart, at 18–21-week gestation is mandatory to exclude major CA.