More than one-third of U.S. women are obese, and the prevalence of obesity in childhood has increased. Excessive gestational weight gain and obesity are independent risk factors for maternal and fetal complications of pregnancy and may very well be implicated in the epidemic of childhood obesity currently seen in the U.S. There are many pregnancy related complications associated with obesity, including miscarriage, infertility and congenital anomalies as well as a variety of late-pregnancy related complications. Additionally, obesity can predispose to the development of fetal macrosomia which can lead to childhood obesity. This article reviews the effects of obesity on pregnancy and potential methods of prevention.