Diabetes mellitus is a major cause of perinatal morbidity and mortality, and of maternal morbidity. Following correct dietary advice during and after pregnancy will help to achieve good diabetic control and reduce the risk of complications. Standard advice for healthy eating should be followed and women with diabetes should eat meals at regular times and in regular amounts, and starchy snacks. The aim is to achieve good control of blood glucose and avoid both hypoglycaemia and peaks after food intake. Weight should be discussed and folic acid 5 mg daily advised before conception and in the first trimester to reduce the increased risk of neural tube defects in the baby.