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.

Data for this retrospective cohort study were obtained from opioid-exposed infants born at Vanderbilt University Medical Center in 2018. Six commonly used clinical and surveillance definitions of opioid exposure and NAS were applied to the study population and evaluated for accuracy in assessing clinical withdrawal.

A total of 121 opioid-exposed infants met the criteria for inclusion in our study. The proportion of infants who met criteria for NAS varied by predefined definition, ranging from 17.4% for infants who received morphine to 52.8% for infants with the diagnostic code for opioid exposure. Twenty-eight infants (23.1%) received a clinical diagnosis of NAS by a medical provider, and 38 (34.1%) received the diagnostic code for NAS at discharge.

We found significant variability in the incidence of opioid exposure and NAS among a single-center population using 6 common definitions. Our findings suggest a need to develop a gold standard definition to be used across clinical, research, and public health surveillance settings.