The care of pre-existing diabetes during pregnancy is complex and the remit of secondary care, but much can be done by primary care staff to ensure that pregnant women and their babies are safely on the right track by the time pregnancy is confirmed. In this article, we explore how to provide women with pre-existing diabetes with detailed and accurate preconceptual advice. Work needs to begin before contraception is discontinued to significantly reduce the risks for both mother and baby. In women with gestational diabetes, practice nurses can also be proactive postnatally, preventing progression to type 2 diabetes.