Across the reproductive spectrum, obesity is associated with greater risks for adverse health outcomes, including higher rates of infertility, subfertility, early pregnancy loss, fetal deaths and stillbirths, congenital anomalies, and pregnancy complications. The excess reproductive morbidity associated with obesity may increase with longer duration, making the current trends among children and young adults particularly critical in terms of their future reproductive potential. Obese women have a lower chance of pregnancy following in vitro fertilization (IVF), require higher dosages of gonadotropins, and have reduced rates of implantation, clinical intrauterine gestation, and live birth rates and increased rates of pregnancy loss, as well as greater risks for prematurity and preeclampsia even when stratified by plurality. Racial and ethnic differences by overweight and obesity in IVF outcomes have been reported. Compared with normal-weight women, failure to achieve a clinical intrauterine gestation is significantly more likely among obese women overall, normal-weight and obese Asian women, normal-weight Hispanic women, and overweight and obese Black women. Among women who do conceive, compared with normal-weight women, failure to achieve a live birth is significantly more likely among overweight and obese women overall, and among overweight and obese Asian women, overweight and obese Hispanic women, and normal-weight and obese Black women. Although weight loss should theoretically be the first line of therapy for obese women, other lifestyle factors, such as regular physical exercise, elimination of tobacco use and alcohol consumption, and stress management, may be of more immediate benefit in achieving conception. (C) 2017 by American Society for Reproductive Medicine.