To determine how characteristics of pregnancy, birth, and early infancy are related to offspring obesity at three critical developmental periods. Mothers were followed through pregnancy and 10-15 years after. Offspring data were obtained through medical record review. Maternal and offspring characteristics were examined to predict obesity in childhood (ages 4-5 years), adolescence (ages 9-14 years), and early adulthood (ages 19-20 years). The original cohort included 802 children born to 795 women. Children who were twins, who had died, or whose mothers had died were excluded (n=25). Medical records of 68.5% of the remaining 777 children documented a height and weight at childhood, adolescence, or early adulthood. Relative risks (RRs) to predict obesity at early adulthood were 12.3 for childhood and 45.1 at adolescence. RRs were also significant to predict obesity at early adulthood between the mother's obesity at prepregnancy (RR=6.4), 4-5 years postpregnancy (RR=6.3), and 10-15 years postpregnancy (RR=6.2). Excluding these variables from the multivariate models and adjusting by gender, birth insurance, and mother's marital status at delivery, the best model to predict obesity at childhood included birth weight, weight gain in infancy, and delivery type. At adolescence, it included maternal pregnancy smoking status, gestational weight gain, and weight gain in infancy, and in early adulthood, included maternal pregnancy smoking status, gestational weight gain, and birth weight. Maternal pregnancy smoking status, gestational weight gain, and weight gain in infancy have long-term effects on offspring. Maternal obesity is the strongest predictor of obesity at all times studied.