The Johns Hopkins trial also found that infants exposed to buprenorphine were hospitalized for less time than infants exposed to methadone. However, the study had a relatively small sample size with only 175 participants, 86 of whom received buprenorphine, leaving scientists with many unanswered questions.

In the current study, lead author Elizabeth Suarez, PhD, who was a postdoctoral scholar at Brigham and Women’s Hospital when the study was conducted, assessed exposure to buprenorphine and methadone in early pregnancy (through gestational week 19), late pregnancy (gestational week 20 through the day before delivery) and the 30 days before delivery (when drug exposure affects neonatal abstinence syndrome).  

Results showed that neonatal abstinence syndrome occurred in 52% of infants exposed to buprenorphine in the 30 days before delivery and in 69.2% of those exposed to methadone. Preterm birth, when a baby is born before 37 weeks of pregnancy, occurred in 14.4% of infants exposed to buprenorphine in early pregnancy and in 24.9% of babies exposed to methadone during the same time frame. 

Greater birth weight with buprenorphine

Twelve percent of babies whose mothers took buprenorphine in early pregnancy were small for their gestational age, compared with 15.3% of those exposed to methadone. Finally, 8.3% of infants exposed to buprenorphine in early pregnancy had an abnormally low birth weight, versus 14.9% of those exposed to methadone.

The researchers found that exposure to buprenorphine versus methadone did not affect whether babies were delivered by Cesarean section, or if the mother experienced life-threatening medical conditions caused by or aggravated by the pregnancy. They also considered many potential confounding variables, including the mother’s mental health, any chronic coexisting conditions, other medication use, social issues such as homelessness and domestic violence, and individuals’ demographics. 

“We were able to generate precise estimates regarding the beneficial effects of buprenorphine,” Bateman said. “It’s a clear suggestion that these are causal effects and that they’re not confounded by patient characteristics that are different between the two groups.”

The hope is that the research will help providers select the proper treatment for pregnant women suffering from opioid addiction.  

“The choice of treatment for opioid use disorder really needs to be individualized,” Bateman said. “Some patients may benefit from buprenorphine, and some may benefit from methadone. But all things being equal, our data suggests that obstetrical outcomes are better in patients who are treated with buprenorphine during pregnancy compared with methadone.”

The research was funded by the National Institute on Drug Abuse (grant R01DA049822).