Our objective was to test the hypothesis that intrauterine exposure to gestational diabetes [GDM] predicts childhood growth independent of the effect on infant birthweight. We conducted a prospective analysis of 28,358 mother-infant pairs who enrolled in the National Collaborative Perinatal Project between 1959 and 1965. The offspring were followed until age 7. Four hundred and eighty-four mothers (1.7%) had GDM. The mean birthweight was 3.2 kg (range 1.1-5.6 kg). Maternal characteristics (age, education, race, family income, pre-pregnancy body mass index and pregnancy weight gain) and measures of childhood growth (birthweight, weight at ages 4, and 7) differed significantly by GDM status (all P < 0.05). As expected, compared to their non-diabetic counterparts, mothers with GDM gave birth to offspring that had higher weights at birth. The offspring of mothers with GDM were larger at age 7 as indicated by greater weight, BMI and BMI z-score compared to the offspring of mothers without GDM at that age (all P < 0.05). These differences at age 7 persisted even after adjustment for infant birthweight. Furthermore, the offspring of mothers with GDM had a 61% higher odds of being overweight at age 7 compared to the offspring of mothers without GDM after adjustment for maternal BMI, pregnancy weight gain, family income, race and birthweight [OR = 1.61 (95%CI:1.07, 1.28)]. Our results indicate that maternal GDM status is associated with offspring overweight status during childhood. This relationship is only partially mediated by effects on birthweight.