Evaluating Definitions for Neonatal Abstinence Syndrome.

National estimates indicate that the incidence of neonatal abstinence syndrome (NAS), a postnatal opioid withdrawal syndrome, increased more than fivefold between 2004 and 2016. There is no gold standard definition for capturing NAS across clinical, research, and public health settings. Our objective was to evaluate how different definitions of NAS modify the calculated incidence when applied to a known population of opioid-exposed infants.