Pregnant women with diabetes are almost four times more likely to have a baby with a birth defect, according to research published in Diabetologica.
Experts found a higher risk of infants suffering serious problems if their mothers had Type 1 or Type 2 diabetes, compared with women without the condition.
The range of birth defects included problems with the nervous system (such as spina bifida), digestive, musculoskeletal and cardiovascular defects and urinary disease.
Diabetics had a 7 per cent risk of a having a baby with a birth defect, compared with about 2 per cent in women without diabetes.
The chance of a birth defect was lowest in women who had blood glucose levels within the normal range at the start of pregnancy.
Researchers analysed more than 401,000 pregnancies, including 1,677 in women with diabetes.