Symptoms of Neonatal Abstinence Syndrome (NAS) can be attributed largely to dysfunction of the autonomic nervous system in opiate exposed neonates. Vagal tone is a readily available measure of autonomic nervous system functioning. NAS is a widely variable disorder with poorly understood pathophysiology; while all opiate exposed infants will exhibit some signs and symptoms of NAS, only approximately ½ have severe enough symptoms to require pharmacologic therapy. This research seeks to determine the relationship between infant vagal tone and NAS severity. The determination of a link between newborn vagal tone and NAS severity could result in the prediction of infants at risk for severe NAS and provide these infants and mothers with intensified services and early treatment, thereby shortening the course of NAS in the infant.