Background: Anxiety disorders are thought to have their origins in early childhood, though they have not yet been studied as a potential outcome of impaired fetal growth, which has been implicated in the developmental etiologies of many psychopathologies. This study investigated the association between indicators of fetal growth and the development of generalized anxiety disorder (GAD). Methods: Indicators of fetal growth, including birth weight (BW) and ponderal index (PI), were assessed among 682 offspring of participants in Providence, Rhode Island, site of the Collaborative Perinatal Project. Participants were interviewed as adults, and their lifetime histories of GAD were assessed using the Diagnostic Interview Schedule. We used Cox regression to estimate the association between fetal growth indicators and development of GAD. Results: The lifetime risk of GAD differed between infants in the highest category of BW, PI, and all others. Newborns with birth weights below 3.5 kg (hazard ratio, HR: 2.38; CI=1.25, 4.55), in the lowest four BW Z-score quintiles (HR=2.49; CI=1.14, 5.45) or a PI in the lowest four quintiles (HR=2.33; CI=1.04, 5.00) had higher lifetime risks of GAD. Conclusion: In contrast to earlier studies on psychiatric outcomes in relation to fetal growth, there was no linear relationship between birth weight and GAD. Although these results generally support the hypothesis that a healthy nutritional fetal uptake, as indicated by BW and PI, is associated with better lifetime mental health, further work is needed to characterize the nature of the association between fetal growth and subsequent psychopathology. Depression and Anxiety, 2010. © 2010 Wiley-Liss, Inc.