At present, more than 60% of American women of childbearing age are either overweight or obese. As the obesity epidemic in the United States and many other countries continues to grow unchecked, there is greater interest in the relationship between obesity and other major health issues. This paper reviews the literature on the relationship between obesity and pregnancy. We begin with a discussion of the relationship between excess body weight and fertility and then turn to the relationship between maternal body weight and pregnancy-related complications. The role of pregnancy as a possible risk factor for the development of obesity is noted. The studies investigating the efficacy of behavioral interventions to control excessive weight gain during pregnancy or help women lose weight after childbirth are then reviewed. The paper concludes with an agenda for future research examining the relationship between obesity and pregnancy.