Opioid use disorder (OUD) during pregnancy is one of the most serious challenges in maternity care today. For years, clinicians treating buprenorphine in pregnancy have relied on a daily sublingual tablet or film placed under the tongue as the standard option. A landmark clinical trial published in JAMA Internal Medicine in March 2026 now gives families and clinicians new, evidence-based reasons to consider a different approach.

This article explains what buprenorphine is, how the two main formulations differ, and what the research means for pregnant women and the people who care for them.

What Is Buprenorphine and Why Is It Used in Pregnancy?

Buprenorphine targets the brain’s opioid receptors to reduce cravings and ease withdrawal symptoms in people with opioid use disorder. Clinicians use it as part of a structured treatment programme during pregnancy to support maternal stability. It also reduces the risks of continued illicit opioid use, including preterm birth, low birth weight, and exposure to unpredictable street drugs such as fentanyl.

Clinicians can deliver buprenorphine in two main ways: as a sublingual formulation taken daily, or as an extended-release injection given weekly or monthly. The daily sublingual version has dominated pregnancy care for years. That is largely because no completed randomised trial had tested the injectable form in pregnant women, until now.

The Study: Key Findings at a Glance

The MOMs trial enrolled 140 pregnant adults with OUD across 13 outpatient sites in the United States between 2020 and 2024. Researchers randomly assigned participants to receive either weekly extended-release buprenorphine injections or their usual sublingual buprenorphine. Clinical teams then followed them through pregnancy and for 12 months after birth.

Researchers measured illicit opioid abstinence during pregnancy through weekly urine drug screens. The results were striking:

Women taking extended-release buprenorphine reached an illicit opioid abstinence rate of 82.5% during pregnancy. The sublingual group reached 72.6%. That gap of nearly 10 percentage points was statistically significant (P = .009).

Women in the extended-release group also had fewer serious adverse events during pregnancy (8.7% vs 26.8%) and postpartum (6.0% vs 18.6%). Fewer of them needed opioid pain medication after delivery (30.2% vs 50.0%). They also reported lower anxiety scores in the months following birth.

Around 28% to 30% of infants in both groups needed opioid treatment for neonatal opioid withdrawal syndrome (NOWS). That figure is lower than the 39% to 48% reported in older studies. Researchers credit this to the fact that most participants were already stable on buprenorphine at enrolment, and to stronger clinical care practices at the participating hospitals.

Why Might Extended-Release Buprenorphine Work Better During Pregnancy?

The pharmacological explanation is fairly simple. Sublingual buprenorphine creates daily peaks and troughs in blood concentration. Levels rise after each dose and drop before the next. Pregnancy also speeds up how the body processes the drug, which pushes those levels lower and makes fluctuation worse. This can leave women more vulnerable to cravings between doses.

Extended-release buprenorphine delivers a steady, consistent level of medication throughout the week. There are no daily peaks or troughs. That stability is likely one of the main reasons the abstinence rates were higher in this group.

What About the Postpartum Period?

The advantage did not carry through after birth. At 12 months postpartum, abstinence rates were nearly identical in both groups: 60.2% versus 59.5%.

Life after birth brings real pressure. Child protective services were involved with 36% of participants in this study. Most women also held custody of their newborns, which means the demands of infant care arrived alongside an already difficult recovery period. Medication discontinuation climbed from around 10% during pregnancy to 35% postpartum in both groups.

Medication alone cannot carry the weight of that. Social, psychological, and practical support all matter enormously in the months after birth.

Buprenorphine in Pregnancy: What the Safety Data Shows

Some clinicians have raised concerns about higher overall buprenorphine exposure with the extended-release formulation compared to equivalent sublingual doses. The trial data offer genuine reassurance.

Infants in the extended-release group showed no significant differences in NOWS treatment rates, hospital stay length, Apgar scores, birth weight, or developmental outcomes at 12 months. The one statistically significant infant finding was a slightly larger average head circumference at birth in the extended-release group (34.0 cm vs 33.4 cm). Both figures sit well within the normal range. All 135 infants with medical record data were born alive and left hospital alive.

On the maternal side, women in the extended-release group did report more medication-related mild adverse events during pregnancy, mainly gastrointestinal symptoms such as nausea and constipation. The authors point out that open-label trials tend to produce higher rates of attributed side effects, particularly for the less familiar treatment. None of these events were severe.

What This Means in Practice

This is the first randomised clinical trial to support weekly extended-release buprenorphine during pregnancy. Before this study, clinicians relied on case reports and small cohort studies to guide decisions about the injectable form.

For healthcare professionals managing buprenorphine in pregnancy, the trial adds evidence that the extended-release formulation:

• Produces higher illicit opioid abstinence rates during pregnancy
• Carries fewer serious maternal adverse events
• Offers a comparable infant safety profile to sublingual buprenorphine
• May suit patients where daily adherence or diversion risk is a concern

The study population was clinically stable. Nearly all participants were already on sublingual buprenorphine at enrolment. Results may not apply to women starting buprenorphine treatment for the first time or those with more complex presentations. The sample was also predominantly White and non-Hispanic, which limits how broadly these findings generalise across different populations.

A Note on Realistic Expectations

The trial reached a completion rate of 98% through pregnancy and 81% through 12 months postpartum. That is high for this type of research. Even so, abstinence rates dropped in both groups after birth. Recovery from opioid use disorder in pregnancy is a long process, not a single outcome that medication alone can secure.

Medication works best as part of something larger: consistent clinical follow-up, honest and non-judgmental conversations about risk, and practical support that meets people where they actually are. The evidence from this trial moves that broader effort forward.

Source: mailchi