In many industrialised countries, one in five women booking for antenatal care is obese. As well as affecting maternal health, maternal obesity may have important adverse consequences for fetal, neonatal and long-term health and well-being. Maternal obesity is associated with a higher risk of stillbirth, elective preterm birth and perinatal mortality. The incidence of severe birth defects, particularly neural tube and structural cardiac defects, appears to be higher in infants of obese mothers. Fetal macrosomia associated with maternal obesity and gestational diabetes predisposes infants to birth injuries, perinatal asphyxia and transitional problems such as neonatal respiratory distress and metabolic instability. Maternal obesity may also result in long-term health problems for offspring secondary to perinatal problems and to intrauterine and postnatal programming effects. Currently, the available interventions to prevent and treat maternal obesity are of limited proven utility and further research is needed to define the effects of maternal weight management interventions on fetal and neonatal outcomes.