<b><i>Background:</i></b> The increasing incidence of childhood obesity is a significant public health challenge, the consequences of which extend across the life course. <b><i>Summary:</i></b> Diet and exercise are clearly the major contributors to childhood obesity, but the factors predisposing to obesity may become established in the womb. Worryingly maternal overnutrition, in particular when it leads to obesity and diabetes, perpetuate an intergenerational cycle of obesity through its effects on placental function and fetal metabolism. This review will address the ways in which the placental lipid and fatty acid transfer may lay the foundations for obesity in the context of maternal overnutrition. <b><i>Key Messages:</i></b> (1) Metabolic changes associated with maternal obesity affect placental nutrient handling. (2) Altered placental nutrient handling may induce pro-adipogenic changes in the fetus, in particular increased fetal insulin. (3) Understanding the effects of maternal obesity on the placenta will aid the development of effective interventions to optimise pregnancy outcomes.