Impaired glucose tolerance in the third trimester of pregnancy.

When the methods and interpretation of glucose tolerance as recommended by the World Health Organisation were applied to 247 patients in the third trimester of pregnancy selected on account of glycosuria, previous large-for-dates offspring, diabetic family history, maternal obesity or a fetus large for gestational age, impaired glucose tolerance (IGT) was found in 20 (8.1%). Patients with IGT were older than those with normal tests: 30.5 +/- 4.8 years (mean +/- S.D.) vs 27.8 +/- 4.8 years (p less than 0.02) and more having IGT had a first degree family history of diabetes (25% vs 10%, p less than 0.05). The majority (15) of the IGT patients then received dietary advice to restrict refined carbohydrate. Post-prandial blood glucose and HbA1 concentrations in these subjects remained within the normal range except for one patient who was treated with insulin. Pregnancy outcome was satisfactory in the patients with impaired tolerance and further studies will be required to assess the clinical significance of IGT in pregnancy.