Project Summary Medical, psychosocial and financial problems associated with prenatal opioid dependency and Neonatal Abstinence Syndrome (NAS) have reached epidemic proportions in the US. Solutions include optimizing the treatment for opioid dependent pregnant women while mitigating the severity of NAS and other neurobehavioral consequences of prenatal opioid exposure. Currently, only methadone maintenance is offered standardly, with more providers prescribing buprenorphine-only in the US due to milder NAS. Methadone treatment, although advantageous for many women, is a difficult choice due to the frequency and severity of the NAS. Buprenorphine-only has a high diversion/abuse potential, is not always readily availble, and can have unpleasant side effects in some women. Buprenorphine-naloxone (B+N) treatment of pregnant women may be an attractive and effective strategy due to the antagonist component, which can result in reduced abuse liability, reduced risk of diversion and increased drug effectiveness by increasing medicaiton adherence, all of which can serve to decrease NAS severity. However, there are currently no published reports that provide a prospective assessment of maternal, fetal and infant functioning with maternal B+N maintenance. Similarly, there is no data available today to support lactation ? another strategy to reduce the severity of NAS expresssion - in B+N maintained women. The purpose of this mechanistic study is to evaluate the effects that maternal B+N maintenance have on the neurobehavioral development of the fetus and infant. To accomplish this, we will study a sample of 120 opioid dependent pregnant women that will receive B+N as part of substance abuse treatment at a comprehensive care treatment facility for pregnant and parenting women with substance use disorders. Fetal neurobehavior and maternal physiology will be assessed, via an established maternal-fetal data acquisition system, at 4 points during gestation: 24, 28, 32 and 36 weeks. Infant birth parameters and NAS spectrum display will be evaluated at birth, and infant neurodevelopment will be assessed during the first month of life. We will compare the neurodevelopment of the B+N-exposed fetuses and infants to that of methadone and buprenorphine-only exposed fetuses and infants. In addition, concentrations of B+N in breast milk, maternal and infant plasma among breastfeeding women maintained on B+N will be determined. NAS parameters and neurobehavioral profiles of B+N breastfed infants will be compared to B+N exposed formula fed infants.