Young, White pregnant woman with light brown hair sitting on bed and holding head to represent having preeclampsia, a condition of pregnancy involving high blood pressure
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The offspring of pregnant women with opioid addiction are less likely to have developmental malformations at birth if exposed to buprenorphine compared with methadone.

Led by Brigham and Women’s Hospital and Harvard Medical School, the study was published in JAMA Internal Medicine. It showed that the risk for various congenital malformations was 18–45% lower in the children of women given buprenorphine compared with those given methadone during pregnancy.

“The proportion of deliveries affected by opioid misuse or long-term opioid use in the U.S. was estimated to be 8.2 per 1000 in 2017, which represents a 131% increase from 2010,” write pharmacoepidemiologist Elizabeth Suarez, based at Brigham and Women’s Hospital and Harvard Medical School during this study, and colleagues.

“Pregnant patients with opioid use disorder are strongly recommended to receive treatment with buprenorphine or methadone to reduce the risk of overdose during pregnancy, limit opioid exposure, and prevent withdrawal symptoms.”

The choice of the medication to prescribe to pregnant women with opioid use disorder can be influenced by many factors. Previous research suggests buprenorphine use may be linked to fewer congenital malformations compared with methadone, but few statistics are available to back this theory up.

The current study included 9514 pregnancies where the mother was prescribed first-trimester buprenorphine and 3846 where they were given methadone. The researchers recorded rates of different birth defects and compared numbers between the two groups.

Overall, the rate of birth defects in the U.S. is around three percent or one in 33 babies. In this study, the overall rate of congenital birth defects in the buprenorphine group was 5.1% and 6.1% in the methadone group.

When the two groups were compared, babies exposed to buprenorphine had a 37% lower risk of cardiac malformations, a 35% lower risk of oral cleft palate defects and a 45% lower risk of clubfoot than those exposed to methadone.

Following additional analysis, the researchers also found a lower risk of neurological, urinary and limb malformations in the buprenorphine group, although those in this group did appear to have a higher risk of gastrointestinal malformations than those in the methadone group.

Suarez and colleagues note that while these results are informative, they do not necessarily exclude methadone as a treatment for pregnant individuals with opioid use disorder.

“The small increase observed in the risk of malformations with methadone use compared with buprenorphine likely does not exclude methadone as the best treatment choice for some pregnant individuals, particularly those on stable treatment prior to pregnancy or patients who do not respond well to buprenorphine,” they write.

“The ultimate goal remains to ensure continued access to effective medication for opioid use disorder for a given patient during pregnancy as well as the postpartum period; this requires a careful trade-off between comparative safety and other determining factors such as treatment access, patient preference, treatment response, and the likelihood of retention in treatment.”

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