Pregnancy hyperglycaemia can lead to foetomaternal complications. Normoglycaemia with exercise, diet and/or insulin can alter outcomes. The insulin requirement itself may alter outcomes independently. Two hundred and forty patients of pregnancy with diabetes mellitus were selected of which 176 belonged to gestational diabetes mellitus and 64 pregestational diabetes mellitus groups. Insulin requirement of pregestational diabetes mellitus group was 1.8 times higher than the gestational diabetes mellitus group. There were no insulin related increased complications in either group. The foetal complications were higher in pregestational diabetes mellitus group (62.5%) than in the gestational diabetes mellitus group (27.3 and 40% in < 15 units or > or = 15 units insulin requirement respectively). The terminal glycaemic parameters (fasting plasma glucose, 2 hours postprandial plasma glucose, HbA1C%) were not different in case of gestational diabetes mellitus between those with and without foetal complications, except for fasting plasma glucose where 'with complications' fasting plasma glucose was lower than without (79.4 +/- 13.14 versus 75.28 +/- 3.68 mg/dl). For pregestational diabetes mellitus patients those without complications had a significantly lower level of all the parameters (fasting plasma glucose 69.75 +/- 0.5 versus 122 +/- 14.14 mg/dl, postprandial plasma glucose 95 +/- 7.4 versus 131.5 +/- 12.02 mg/dl; HbA1C 6.8 +/- 0.28 versus 7.3 +/- 3.6%) compared with those having complications. Maternal complications could not be segregated as all the subgroups had a very incidence of caesarean section (60%-100%). However, when lower segment caesarean section was excluded and maternal complications segregated, for gestational diabetes mellitus patients, only fasting plasma glucose was significantly lower in cases without complications while in pregestational diabetes mellitus patients the fasting plasma glucose as well as HbA1C were significantly lower in cases without complications.