Background: Offspring of mothers with diabetes mellitus (DM) during pregnancy may be at high risk for developmental alterations. This study aimed to identify the effects of maternal pre-and gestational diabetes on the body mass index of infants and children at two, four, six, and eight years of age. Methods: We studied children of mothers with type 1, type 2, and gestational diabetes and a control group. Maternal and neonatal variables were analyzed for associations with children overweight/obesity. Results: Mothers with DM were older than controls (32 ± 6 vs. 22 ± 6 years, p < 0.001). The frequency of preeclampsia in mothers with DM was 28%. Gestational age and weight at birth were lower in infants from the groups of mothers with DM in comparison with controls (32.8 ± 3.1 vs. 36.4 ± 2.2 weeks, p < 0.001, and 1,637 ± 600 vs. 2,208 ± 518 g, p < 0.001, respectively). At 8 years of age, 47% of the offspring of mothers with DM type 2 had overweight/obesity (odds ratio (OR 8.25) 95% confidence interval (CI) 1.3-51, p = 0.01), while 27% of offspring of mothers with type 1 DM had overweight/obesity, and 10% of offspring of mothers with gestational diabetes presented overweight/obesity. Conclusions: Offspring of pre-gestational DM mothers have a higher risk to develop overweight/obesity, as was observed with follow-up until school age, for which they require continuous vigilance.