Birthweight and the risk for type 2 diabetes mellitus in adult women.

BACKGROUND Previous reports have suggested an association between birthweight and type 2 diabetes mellitus. OBJECTIVE To investigate the association between birthweight and type 2 diabetes in a large cohort of adult women, taking into account potential explanatory factors in childhood and adult life. DESIGN Cohort study. Birthweight was ascertained at the end of follow-up. SETTING The Nurses' Health Study, a cohort of 121,701 U.S. women born from 1921 to 1946 who have been followed since 1976. PARTICIPANTS 69,526 women in the Nurses' Health Study who were free of diabetes at baseline and reported their own birthweight on the 1992 questionnaire. MEASUREMENT 2123 cases of confirmed type 2 diabetes diagnosed from 1976 to 1992. RESULTS Low birthweight was associated with increased risk for type 2 diabetes. Age-adjusted relative risks suggested a reverse J-shape association between birthweight and risk for type 2 diabetes. However, after adjustment for adult body mass index and maternal history of diabetes, an inverse association across the entire range of birthweight became apparent; compared with the reference group, relative risks by ascending birthweight category were 1.83 (95% CI, 1.55 to 2.16) for birthweight less than 5.0 lb, 1.76 (CI, 1.49 to 2.07) for birthweight 5.0 to 5.5 lb, 1.23 (CI, 1.11 to 1.37) for birthweight 5.6 to 7.0 lb, 0.95 (CI, 0.82 to 1.10) for birthweight 8.6 to 10.0 lb, and 0.83 (CI, 0.63 to 1.07) for birthweight of more than 10 lb (P for trend < 0.001). Adjustment for ethnicity, childhood socioeconomic status, and adult lifestyle factors did not substantially alter this association. The association between birthweight and risk for type 2 diabetes was strongest among women whose mothers had no history of diabetes. CONCLUSIONS Birthweight is inversely associated with risk for type 2 diabetes during adulthood. Examination of prenatal nutrition and other potential in utero determinants of both birthweight and risk for type 2 diabetes may yield new means to prevent type 2 diabetes.