In a cohort of women followed up for adolescent idiopathic scoliosis, we assessed the association between exposure to ionizing radiation from diagnostic radiography received in adolescence and subsequent adverse reproductive outcomes in adulthood. We estimated risk for unsuccessful attempts at pregnancy, spontaneous abortions, low birthweight (<2,500 gm), congenital malformations, and stillbirths according to dose to the ovaries. We used regression models for binary and continuous outcomes, accounting for key covariates and for clustering in the data that arose from women having multiple pregnancies. Risks in the adolescent idiopathic scoliosis cohort were higher than in the reference group for unsuccessful attempts at pregnancy [adjusted odds ratio (OR) = 1.33; 95% confidence interval (CI) = 0.84-2.13], spontaneous abortions (OR = 1.35; 95% CI = 1.06-1.73), and congenital malformations (OR = 1.20; 95% CI = 0.78-1.84), but the odds ratios did not increase monotonically by dose to the ovaries. There were fewer stillbirths (OR = 0.38; 95% CI = 0.15-0.97) and low-birthweight infants in the adolescent idiopathic scoliosis cohort (OR = 0.84; 95% CI = 0.59-1.21). Nevertheless, when the analysis of low birthweight was restricted to the adolescent idiopathic scoliosis cohort, the adjusted odds ratios were found to increase by quartiles of dose (median dose of 0.69 cGy): 1; 1.43 (95% CI = 0.54-3.90); 2.24 (95% CI = 0.89-5.94); and 2.34 (95% CI = 1.02-5.62). We also found that the adjusted mean birthweight decreased with increasing dose by 37.6 gm per cGy (standard error = 23.5 gm per cGy). Associations between adverse reproductive outcomes and radiotherapy have been observed previously, but this is the first study in which an association with birthweight has been found with diagnostic radiography.