The objectives of this study were to evaluate the long-term effect of the diabetic pregnancy on Pima Indian offspring and to see how the prevalence of diabetes during pregnancy is influenced by early life events, such as birth weight and type of infant feeding, that are known to influence the prevalence of diabetes in nonpregnant Pima adults. A modified 75-g oral glucose tolerance test was administered to women during each pregnancy. These women and, from the age of 5 years, their children were followed biennially with a standardized examination that includes measurement of height and weight and a standard 75-g oral glucose tolerance test administered in the morning after an overnight fast. We found that diabetes during pregnancy is a major risk factor for diabetes and hyperglycemia in the offspring. Diabetes in the next generation is less common among breast-fed children (6.9 and 30.1% among offspring of nondiabetic and diabetic women, respectively) than among bottle-fed children (11.9 and 43.6%, respectively). The prevalence of diabetes during pregnancy is influenced by conditions, such as birth weight, known to influence the prevalence of diabetes in this population in general. The highest rates of diabetes during pregnancy at 25-34 years of age (25%) were found among women with a birth weight below 2.5 kg. The infant of the woman with diabetes during pregnancy is at risk of becoming obese and of developing type 2 diabetes at a young age. The prevalence of diabetes in women of childbearing age is influenced by factors occurring early in life (i.e., birth weight and type of infant feeding). Whether or not the long-term adverse outcomes, including diabetic pregnancies in the next generation, can be lessened or prevented by meticulous control of diabetes during pregnancy, careful attention to intrauterine growth, or more general infant breast-feeding remains unknown.