The National Institute of Child Health and Human Development held a workshop on September 12-13, 2005, to summarize the risks for adverse pregnancy outcomes after assisted reproductive technology (ART), develop an approach to counseling couples regarding these risks, and establish a research agenda. Although the majority of ART children are normal, there are concerns about the increased risk for adverse pregnancy outcomes. More than 30% of ART pregnancies are twins or higher-order multiple gestations (triplets or greater) and more than one half of all ART neonates are the products of multifetal gestations, with an attendant increase in prematurity complications. Assisted reproductive technology singleton pregnancies also demonstrate increased rates of perinatal complications-small for gestational age infants, preterm delivery, and perinatal mortality-as well as maternal complications, such as preeclampsia, gestational diabetes, placenta previa, placental abruption, and cesarean delivery. Although it is not possible to separate ART-related risks from those secondary to the underlying reproductive pathology, the overall increased frequency of obstetric complications, including preterm birth and small for gestational age neonates, should be discussed with the couple. Significant gaps in knowledge were identified, and the basic science and clinical and epidemiologic research required to address these gaps is outlined.