The purpose of this study was to assess, in women with gestational diabetes mellitus (GDM): 1) metabolic control during labour using a standardised protocol; 2) the influence of therapy during pregnancy in intrapartum metabolic control and insulin requirements; and 3) the impact of maternal glycaemia during labour on neonatal hypoglycaemia. An observational study of 85 women with GDM (54 insulin-treated) was performed. Intrapartum metabolic management included i.v. glucose and insulin infusions, urinary ketone measurement and hourly capillary blood glucose (CBG) monitoring. Mean CBG from arrival to delivery was 4.7 +/- 1.1 mmol/l with 83% of mean CBG values within the target range (2.8-6.9 mmol/l). Mean CBG and insulin requirements were unrelated to therapy during pregnancy, but hypoglycaemia (CBG<2.8 mmol/l) was more frequent in women receiving insulin during pregnancy (40.7 vs 19.4 %, p<0.01). In several logistic regression models, CBG during labour was predictive of neonatal hypoglycaemia. We conclude that in women with GDM, the use of a standardised intrapartum management protocol is associated to fair metabolic control, that insulin requirements during labour are unrelated to therapy during pregnancy and that high CBG during labour increases the risk of neonatal hypoglycaemia.