Prior studies have shown an increased vulnerability among males, to adverse outcomes during the postnatal period. The majority of children exposed to opioids and other medication in utero develop a neonatal abstinence syndrome (NAS), yet individual predisposition for NAS is poorly understood. This investigation examines the role of neonatal sex in the postnatal period, for neonates exposed to standardized opioid maintenance treatment in utero with a focus on the neonatal abstinence syndrome (NAS) regarding severity, medication requirements and duration.
Patients and Methods
This is a secondary analysis of data collected in a prospective randomized, double-blind, double-dummy multi-center trial examining the comparative safety and efficacy of methadone and buprenorphine during pregnancy (Maternal Opioid Treatment: Human Experimental research MOTHER – study). 131 neonates born to opioid-dependent women randomized at six US sites (n=74) and one European site (n=37) were analyzed. Sex-based differences in birth weight, length, head circumference, NAS duration, NAS severity, and treatment parameters of full-term neonates were assessed.
Males had a significantly higher birth weight (p=0.027) and head circumference (p=0.017) than females, with no significant sex difference in rates of preterm delivery. No significant sex-related differences were found for NAS development, severity, duration, or medication administered with non significant differences in concomitant drug consumption during pregnancy (p =0.959).
This unique prospective study shows similar postnatal vulnerability for both sexes, suggesting that factors other than sex are the major determinants of clinically significant NAS.