One hundred twelve women with impaired glucose tolerance (IGT) diagnosed by intravenous glucose tolerance test (IVGTT) after pregnancy were followed up for a period of up to 22 yr (mean 12.9 yr). About one-third have been treated with chlorpropamide and the others by diet only. At the final assessment, approximately 35% had abnormal intravenous glucose tolerance and less than 7% overt diabetes. Chlorpropamide did not prove significantly more effective than diet only. Factors associated with deterioration in glucose tolerance were age at diagnosis and follow-up and the initial fasting plasma glucose (FPG) level (≥5.8 mM), but obesity was less important, although it was associated with an increased rate of vascular complications. Tests for islet cell antibodies (ICA) were weakly positive in 12.5% of 72 subjects and in only 0.5% of an unselected population; they did not correlate with the final state of glucose tolerance. Only three patients developed insulindependent diabetes (IDDM) and did so before the ICA study was started. A comparison is made between the results reported by O'Sullivan in patients diagnosed as having gestational diabetes, only 2% of whom still had abnormal oral glucose tolerance postpartum, and the results of our patients, all of whom had IGT after pregnancy. In spite of differences of technique and in the populations studied, the prevalence of IGT and overt diabetes at follow-up was significantly less in the Aberdeen series, who were initially a higher risk group. It seems probable that this is mainly attributable to dietary treatment in the follow-up period as O'Sullivan's cases were treated only during pregnancy.

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