The concepts of sensitivity, specificity, and predictive value can be used to assess patterns of birth defects associated with human teratogens. Although sensitivity of any single defect is generally low for many known teratogens, the presence of specific defect combinations is usually predictive of the teratogen. To evaluate the patterns of birth defects associated with diabetic embryopathy, a sensitivity-specificity analysis was performed on 4929 infants with major defects ascertained by the population-based Metropolitan Atlanta Congenital Defects Program between 1968 and 1980. By reviewing hospital records, maternal insulin-dependent diabetes mellitus was confirmed in 26 infants. Patterns of defects were evaluated among infants born to mothers with insulin-dependent diabetes mellitus and compared with the rest of the Metropolitan Atlanta Congenital Defects Program case population. Multiple logistic regression analysis was used to assess defect combinations that predict for insulin-dependent diabetes mellitus. Of 26 infants, 8 had multiple defects. However, most defects and their combinations were poorly sensitive and predictive for insulin-dependent diabetes mellitus. The predictive value for insulin-dependent diabetes mellitus was greatest for the combination of vertebral and cardiovascular anomalies (6.5%). Also, several pathogenetic mechanisms were noted among patients with insulin-dependent diabetes mellitus, such as cell migration defects, cell death events, deformations, and cardiac flow lesions. The inability to find a clear-cut phenotype for diabetic embryopathy may be due to several etiologic factors and mechanisms associated with diabetic embryopathy.