Objective: To review data on the long‐term effects of prenatal exposure to the diabetic intrauterine environment in the Pima Indians of Arizona. This population has high rates of Type 2 diabetes mellitus that has a strong genetic component and develops at young ages.

Methods: Since 1965, Pima Indians at least 5 years old participated in a study of diabetes and its complications. This study consisted of biennial examinations with measurements of obesity and glucose tolerance and of glucose tolerance testing during pregnancy. The longitudinal nature of the study has permitted comparisons of data collected on children and young adults whose mothers were tested during pregnancy.

Results: Offspring of women who had diabetes during pregnancy were more obese and had a higher prevalence of Type 2 diabetes. Exposure to the diabetic intrauterine environment was responsible for about 40% of Type 2 diabetes in 5–19‐year‐old children between 1987 and 1996—approximately twice the attributable risk found between 1967 and 1976. Over 70% of persons with prenatal exposure have Type 2 diabetes at 25–34 years of age.

Conclusions: The effects of the diabetic pregnancy can be thought of as a vicious cycle, with consequences for the offspring extending well beyond the neonatal period. The young woman whose mother had diabetes during pregnancy is at risk of perpetuating the cycle by developing diabetes by her childbearing years. In this population, much of the increase in childhood Type 2 diabetes can be attributed to the diabetic intrauterine environment, which may be a factor in the alarming rise of this disease nationally. J. Matern.‐Fetal Med. 2000; 9:83–88. © 2000 Wiley‐Liss, Inc.