Association of medication-assisted treatment and short acting opioids with newborn head circumference and birth weight

Objective We compared the association of methadone, buprenorphine, and short-acting opioid exposure with newborn head circumference (HC) and birth weight (BW), and evaluated gestational age (GA) as a mediator. Study design We included newborns born 2013–2018 identified by neonatal abstinence syndrome diagnosis code ( N = 572) and birthday-matched unexposed controls ( N = 571). Linear regressions of opioid exposure with HC and BW controlled for tobacco, marijuana, cocaine, gabapentin, cesarean section, Medicaid, and newborn sex, with mediation analysis by GA. Result Methadone was associated with 0.81 cm lower HC (95% CI = −1.22, −0.40) and 0.23 kg lower BW (95% CI = −0.35, −0.10) with approximately 24% and 41% mediated by GA, respectively. Buprenorphine and short acting opioids were not associated with HC or BW. Conclusion Methadone exposed newborns have smaller HC and lower BW not fully attributable to younger GA, suggesting a direct effect of methadone on intrauterine growth. Exploration of potential developmental consequences of this is urgently needed.