In women with preexisting diabetes and nephropathy or microalbuminuria, it is important to deliver careful preconception counselling to assess the risk for the mother and the foetus, for optimizing glycaemic status and to adjust medical treatment. If serum creatinine is normal in early pregnancy, kidney function is often preserved during pregnancy, but complications such as severe preeclampsia and preterm delivery are still common. Perinatal mortality is now comparable with that in women with diabetes and normal kidney function. Besides strict glycaemic control before and during pregnancy, early and intensive antihypertensive treatment is important to optimize pregnancy outcomes. Methyldopa, labetalol, nifedipine and diltiazem are considered safe, whereas angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers should be stopped before or at confirmation of pregnancy. Supplementation with folic acid in early pregnancy and low-dose aspirin from 10 to 12 weeks reduces the risk of adverse pregnancy outcomes. During breastfeeding, several ACE inhibitors are considered safe.