Obesity at the start of pregnancy has been rising worldwide, increasing the risk of maternal complications. We reviewed the independent effects of maternal obesity during pregnancy on neonatal adverse outcomes and the risk of childhood obesity and adverse cardio-metabolic profiles. We searched MEDLINE for papers published in English between December 2007 and November 2017, focusing primarily on human studies published in the last five years. However, we also chose to highlight examples derived from model animals that could bring mechanistic insight and preventive and therapeutic avenues. Our review showed that maternal obesity had independent effects on neonatal adverse outcomes such as macrosomia, perinatal mortality and birth defects. Maternal obesity alone increased the risks for adverse neonatal outcomes, including macrosomia, perinatal mortality, induced preterm birth and birth defects. In association with excess gestational weight gain, mainly early in pregnancy, increased the risks of childhood obesity, higher fat mass and, to a smaller extent, adverse cardio-metabolic profiles. Animal models highlighted sexually dimorphic responses to maternal obesity. Maternal obesity induced serious adverse neonatal effects and was associated with childhood obesity in their offspring. The peri-conceptional period is critical for metabolic programming and obese women need close monitoring from conception