IntroductionEstimating Neonatal Abstinence Syndrome (NAS) and prenatal substance exposure rates in Medicaid can help target program efforts to improve access to services.MethodsThe data for this study was extracted from the 2016–2020 Transformed Medicaid Statistical Information System (T-MSIS) Analytic Files (TAF) Research Identifiable Files (RIF) and included infants born between January 1, 2016 and December 31, 2020 with a either a NAS diagnosis or prenatal substance exposure.ResultsBetween 2016 and 2020, the estimated national rate of NAS experienced a 18% decline, while the estimated national rate of prenatal substance exposure experienced a 3.6% increase. At the state level in 2020, the NAS rate ranged from 3.2 per 1000 births (Hawaii) to 68.0 per 1000 births (West Virginia). Between 2016 and 2020, 28 states experienced a decline in NAS births and 20 states had an increase in NAS rates. In 2020, the lowest prenatal substance exposure rate was observed in New Jersey (9.9 per 1000 births) and the highest in West Virginia (88.1 per 1000 births). Between 2016 and 2020, 38 states experienced an increase in the rate of prenatal substance exposure and 10 states experienced a decline.DiscussionEstimated rate of NAS has declined nationally, but rate of prenatal substance exposure has increased, with considerable state-level variation. The reported increase in prenatal substance exposure in the majority of US states (38) suggest that substances other than opioids are influencing this trend. Medicaid-led initiatives can be used to identify women with substance use and connect them to services.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10995-023-03670-z.