Obesity in women of reproductive age is increasing at an unprecedented rate in western societies. Maternal obesity is associated with an unequivocal increase in maternal and fetal complications of pregnancy. Excessive maternal weight gain in pregnancy also appears to be an independent risk factor, regardless of prepregnancy weight. Few guidelines exist regarding appropriate weight gain in pregnancy in obese women. We review the association of maternal obesity with pregnancy complications. We also suggest that appropriate diet and lifestyle intervention can enable women with severe prepregnancy obesity to safely achieve quite strict targets for limited weight gain in pregnancy.