The developed and developing worlds are experiencing an epidemic of obesity and associated predisposition to diabetes. This epidemic places a major drain on health care resources. It is now clear that maternal obesity and gestational diabetes have major adverse effects on the developing fetus that lead to increased neonatal morbidity and mortality, as discussed elsewhere in this issue. Obesity in pregnancy and gestational diabetes represent a special problem, not only as a result of their immediate adverse effects on maternal health and pregnancy outcome, but also because of growing evidence for their persistent and deleterious effects on the developing child.