Study participants are recruited into the study at Tampere University Hospital Maternity Ward when their daily insulin dose exceeds 30 IU. Randomization is done at 37th gestational week, if vaginal delivery is planned, and HbA1c is measured. Randomization envelope is opened at the delivery ward when active labour begins and treatment of blood glucose level is carried out accordingly. If insulin dose is 1 IU/kg or more, the participant is treated as in active treament group despite of result of randomization. All neonates will recieve milk substitute after birth in labour ward. Plasma glucose is measured immediately if neonate has symptoms of low blood sugar. If not, plasma glucose is measured approximately two hours after birth and after that every 4 hours until plasma glucose is 3,0 mmol/l or more in three consecutive measurements.