In 2009, the Institute of Medicine (IOM) revised their pregnancy weight gain guidelines, recommending gestational weight gain of 11-20 pounds for women with prepregnancy BMI >30 kg/m(2). We investigated the potential influence of the new guidelines on perinatal outcomes using a retrospective analysis (n = 691), comparing obese women who gained weight during pregnancy according to the new guidelines to those who gained weight according to traditional recommendations (25-35 pounds). We found no statistical difference between the two weight gain groups in infant birth weight, cesarean delivery rate, pregnancy-related hypertension, low birth weight infants, macrosomia, neonatal intensive care unit admissions, or total nursery days. Despite showing no evidence of other benefits, our data suggest that obese women who gain weight according to new IOM guidelines are no more likely to have low birth weight infants. In the absence of national consensus on appropriate gestational weight gain guidelines, our data provide useful data for clinicians when providing evidence-based weight gain goals for their obese patients.