Obesity has reached epidemic proportions in the United States. Along with this increase, weight loss surgeries, known as bariatric procedures, have become increasingly common. This report assesses the incidence of these operations in women of reproductive age and reviews the evidence on the impact of such surgery on fertility, contraception, prepregnancy risk factors, and pregnancy outcomes, including those for neonates. For patients who are severely obese, most nonsurgical treatments-such as diet, exercise, and medications-are not very effective at producing significant weight loss and, more importantly, maintaining weight loss. A recent meta-analysis by Li found that medications, along with diet and other exercise interventions, produce only modest weight loss (5 kg lost at one year). Similarly, controlled studies of diets have shown mostly minimal weight loss. In contrast, observational reports have concluded that surgical treatments for severe obesity result in substantial weight loss that patients are able to maintain over the long term. A recent metaanalysis by Maggard et al reported that bariatric procedures generate, on average, 20-30 kg of weight loss and that the weight loss can be maintained for at least 10 years. A variety of surgical procedures have been used to induce weight loss for obese patients. These procedures result in weight loss via different mechanisms, and some employ a combination of mechanisms. In general, bariatric surgery employs three mechanisms to induce weight loss: (1) restricting the size of the stomach limits the quantity of food a patient can consume at a single meal, (2) malabsorptive procedures decrease the proportion of nutrients that are absorbed from a meal, and (3) a combination of hormonal changes are induced by creating a small gastric pouch (and outlet) along with a proximal bypass. Weight loss procedures are being performed more frequently to treat morbid obesity, with a six-fold increase over a recent 7-year time span; almost half of patients are women of reproductive age. The level of evidence on fertility, contraception, and pregnancy outcomes is limited primarily to case series and case reports. The evidence suggests that fertility improves after bariatric surgical procedures; however, data are too sparse to reach definite conclusions about the degree of improvement in fertility that is achieved. Evidence also suggests that nutritional deficiencies for mother and child are minimal, and maternal and neonatal outcomes are acceptable with laparoscopic adjustable band and gastric bypass as long as adequate maternal nutrition and vitamin supplementation are maintained. The American College of Obstetricians and Gynecologists (ACOG) nominated the topic of this report and provided the following initial list of questions: 1. What is the incidence of bariatric surgery in women of reproductive age? What are the trends in incidence of bariatric surgery in women of reproductive age? 2. What is the evidence that bariatric surgery affects (directly or indirectly) future fertility? 3. What is the evidence that bariatric surgery affects (directly/indirectly) choice of contraception? 4. In patients who have had bariatric surgery, what is the evidence for prenatal risk factors (e.g., of reduced nutrient absorption, unusual weight gain) that may result in poor pregnancy outcomes? 5. What is the evidence that certain management strategies for addressing nutrient absorption and weight gain reduce the risks of poor pregnancy outcomes? 6. For women who have had bariatric surgery, what is the evidence for morbidity and mortality risks for: a) mother and b) neonate? 7. What is the evidence that cesarean section for women who have had bariatric surgery affects the risks of morbidity and mortality for: a) mother and b) neonate?