In normotensive women with Type 1 diabetes and microalbuminuria we previously found preterm delivery (<34 weeks) in 23% of the pregnancies. Antihypertensive treatment was initiated in late pregnancy when preeclampsia was diagnosed and diastolic blood pressure > 90 mmHg. From April 2000 our routine was changed and early antihypertensive treatment with methyldopa was initiated if antihypertensive treatment was given prior to pregnancy, if urinary albumin excretion (UAE) was > 2 g/24 h, or blood pressure > 140/90 mmHg. The present study describes the impact of this more aggressive antiypertensive treatment in the prevalence of preterm delivery.