Incidence of diabetes mellitus in women following impaired glucose tolerance in pregnancy is lower than following impaired glucose tolerance in the non-pregnant state

Impaired glucose tolerance (IGT), which is asymptomatic and requires a glucose tolerance test for detection, is a well-known risk factor for diabetes mellitus, Outside the research setting it is rarely identified in people who lack specific risk factors for diabetes except during pregnancy, at which time screening with an oral glucose challenge is a routine procedure. A 75-g oral glucose tolerance lest was performed during the latter part of pregnancy or during a routine epidemiology survey in 15-39-year-old Pima Indian women with no history of abnormal glucose tolerance. Those with IGT by World Health Organization criteria were included in this study. Diabetes incidence in women was compared between those whose IGT was first detected during pregnancy and those who were not pregnant when IGT was first recognized. Seventeen of 73 pregnant women and 114 of 244 non-pregnant women developed diabetes within 10 years. When controlled for plasma glucose concentration, age body mass index, parity and duration of follow-up, those who were not pregnant were at higher risk of developing diabetes than these who were pregnant (hazard rate ratio = 1.71, 95 % confidence interval = 1.01-2.91). Previous studies had reported that women with IGT during pregnancy are at higher risk of diabetes than women with normal glucose tolerance. This study suggests that: women with IGT during pregnancy are at lower risk than non-pregnant women with a similar plasma glucose concentration who, in the clinical setting, are likely to remain unrecognized.