Gestational diabetes affects 0.6 percent to 15 percent of pregnant women (35). It implies an increased risk of development of impaired glucose tolerance and diabetes (35). Most develop type 2 diabetes, with an incidence of at least 13.8 percent. The incidence of type 1 diabetes is reported to be 0.7 percent to 6.6 percent over 2-11 years. In a study looking at gestational diabetes, the cumulative risk for diabetes and abnormal glucose tolerance was 13.8 percent and 42.4 percent after 11 years versus 0.0 and 2.8 percent in women without diabetes (35). Independent, predictive factors for diabetes were prior hyperglycemia; four abnormal glucose values on the diagnostic OGTT; overt diabetes during pregnancy; two-hour blood glucose > 11.7 mmol/l on the diagnostic OGTT; gesta-tional age at diagnosis < 24 weeks; and prepregnancy body-mass index (BMI) > 26.4 kg/m2 (35). Race is thought to be a risk factor for gestational diabetes (36). Recurrence rates for gestational diabetes have been reported to range from 30 percent to 35 percent in studies looking at predominantly Caucasian populations, to > 50 percent in nonwhite populations (36). Factors predictive of recurrent gestational diabetes include large infant birth weight, prepregnancy weight > 190 pounds, and weight gain between pregnancies (36). The effect of additional pregnancies on the risk of future diabetes is controversial, with some studies suggesting an increased risk and others showing no increase (35). The range of relative risk (RR) for developing diabetes after gestational diabetes, in the literature, is 1.8 to 20.4 (37). In a carefully designed meta-analysis of controlled follow-up studies of women with gestational diabetes, the overall RR for developing diabetes after gestational diabetes was estimated to be 6.0 (95 percent, CI 4.1-8.8), with a population attributable risk of 0.10-0.31 (10 percent to 31 percent of cases of diabetes in parous women are associated with previous diabetes) (37).
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