Type 1 diabetes mellitus in pregnant women increases the risk of adverse outcomes for mother and offspring. Careful preconception counselling and screening is important, with particular focus on glycaemic control, indications for antihypertensive therapy, screening for diabetic nephropathy, diabetic retinopathy and thyroid dysfunction, as well as review of other medications. Supplementation with folic acid should be initiated before conception in order to minimize the risk of fetal malformations. Obtaining and maintaining tight control of blood glucose and blood pressure before and during pregnancy is crucial for optimizing outcomes; however, the risk of severe hypoglycaemia during pregnancy is a major obstacle. Although pregnancy does not result in deterioration of kidney function in women with diabetic nephropathy and normal serum creatinine levels, pregnancy complications such as pre-eclampsia and preterm delivery are more frequent in these women than in women with T1DM and normal kidney function. Rapid-acting insulin analogues are considered safe to use in pregnancy and studies on long-acting insulin analogues have provided reassuring results. Immediately after delivery the insulin requirement declines to approximately 60% of the prepregnancy dose, and remains 10% lower than before pregnancy during breastfeeding.