Though the use of buprenorphine in medication-assisted treatment (MAT) for opioid use disorder (OUD) during pregnancy has shown to have few impacts on fetuses and infants, a new study examining the physiological impact of the drug on pregnant women shows a significant impact on maternal heart rate.

Hendrée Jones, PhD, professor of obstetrics and gynecology and executive director of UNC Horizons at the UNC School of Medicine, is co-author of “Maternal buprenorphine treatment during pregnancy and maternal physiology,” which was published recently in Drug and Alcohol Dependence.

MAT is the recommended therapy for pregnant women with OUD, according to the American College of Obstetrics and Gynecologists. Buprenorphine is commonly preferred over methadone for its low risk to the fetus and its prevention of continued opioid misuse by pregnant women. This is the first known study to expand scientific knowledge on buprenorphine to include its physiological effects on pregnant women.

The research team explored how buprenorphine affects indicators of the autonomic nervous system in a sample of pregnant women with OUD in a comprehensive substance use treatment center. Heart rate and respiratory function were measured to evaluate baseline functioning, heart rate variability measurements represented the parasympathetic nervous system and electrodermal activity represented the sympathetic nervous system. In pregnant women without OUD, the measures are typically stable.

The findings show that the administration of the drug significantly accelerated maternal heart rate and dampened maternal heart rate variability at 24 and 36 weeks, regardless of buprenorphine dose, suggesting the drug impacts the balance of the autonomic nervous system in these women. Cigarette smoking increased the effects of buprenorphine, highlighting the need for incorporating smoking cessation programs into MAT programs for pregnant women with OUD.