our GDM population may reflect a combination of hyperglycaemia, insulin resistance, an elevated BMI and possibly and perhaps most significantly, undiagnosed pre-gestational diabetes. The data in this study must be considered as preliminary, but based on this preliminary data we consider these women to be at an increased risk of having a baby with CHD. Until more detailed data from larger studies is available, we will continue to accept these women as referrals for detailed fetal echocardiography. We would recommend a prospective, multicentre study to identify women at high risk, who may have undiagnosed pregestational type 2 diabetes. In addition we recommend further studies to assess an association between an increased maternal BMI and the incidence of congenital heart disease.