Women with pre-existing diabetes who are planning a pregnancy ideally should receive high-quality, multidisciplinary preconception care in a specialist centre; this has been shown to improve pregnancy outcomes. Optimising glycaemic management is essential prior to conception and throughout pregnancy and breastfeeding to minimise adverse events. Low-dose aspirin is recommended from 12 weeks gestation for prevention of pre-eclampsia. Breastfeeding is highly advantageous in women with pre-existing diabetes; women often need additional support with establishment and maintenance of breastfeeding. High-quality postpartum care and effective contraception are essential.