Prenatal Opioid Exposure May Result in Smaller Brains Among Newborns: Study

Brain sizes could also be affected by opioid addiction treatments like methadone and buprenorphine, researchers warn.

New research indicates that infants exposed to opioids during pregnancy have 5% smaller brain volume than infants not exposed to the painkillers, highlighting ongoing concerns about the long-term effects of the opioid abuse epidemic in the United States.

It has been known for decades that pregnant women who use opioids can give birth to infants with neonatal abstinence syndrome (NAS), which involves a group of conditions that newborns experience when they suffer withdrawal from drugs in the mother’s system, like opioids. The symptoms can include seizures, sleep problems, hyperactive reflexes, congestion, poor feeding, dehydration, vomiting and other side effects.

In addition, using opioids while pregnant is known to affect fetal brain development. However, new findings published in the journal JAMA Pediatrics on April 7, now indicate that prenatal exposure to opioids, including treatment medications like methadone and buprenorphine, can also cause a serious loss of brain volume, gray matter and other portions of the brain.

For the study, researchers from the Children’s National Hospital in Washington, D.C. examined newborns from the Outcomes of Babies with Opioid Exposure study.

The team, led by Dr. Yao Wu, looked at a total of 173 women in the second or third trimester of pregnancy who were exposed to opioids or other opioid addiction medications from 2020 to 2023. These women were then compared with 96 non-using controls from the same period. MRIs were performed on the infants within the first year.

The data indicates infants prenatally exposed to opioids had smaller volume for cortical gray matter, deep gray matter, white matter, cerebellum, brainstem, and the right and left amygdala.

Brain volume among the opioids-exposed infants was 387 cm³ compared to 407 cm³ among the control group. They also had lower cortical volume, 167 cm³ compared to 176 cm³.

Researchers said the smaller volume finding was also true among infants prenatally exposed to drugs specifically used to treat opioid addiction and abuse. The opioid treatments most commonly used by study participants were methadone and buprenorphine, which is present in Suboxone.

Infants exposed to methadone during the prenatal period had significantly smaller white matter volume than controls, 155 cm³ compared to 166 cm³.

Infants exposed to buprenorphine had smaller right amygdala volume compared to controls, 0.51 cm³ vs 0.55 cm³.

The same pattern was also seen for cerebellum matter, deep gray matter and the brain stem. All areas were smaller among infants exposed to opioids or to multiple substances along with opioids. In fact, infants exposed to multiple substances during pregnancy had smaller volumes in more brain regions than opioid-only exposure.

As a result of these findings, the research team determined that infants experienced impaired regional brain growth when exposed prenatally to opioids.

The researchers said this data highlights the vulnerability of the developing brain, especially to harmful substances like opioids. More so, researchers noted the findings suggest reduced brain volume in several areas may be an early biomarker for identifying later neurodevelopmental dysfunction.

These results may help doctors identify infants who should be screened for neurodevelopmental conditions later and help provide resources and support for those families, researchers said.

Prenatal Opioid Exposure

In addition to brain development issues, opioid exposure during pregnancy can cause the fetus to grow poorly, potentially leading to preterm birth, stillbirth, birth defects such as cleft palate and clubbed feet, as well as developmental disorders later in life.

A study published by researchers from Vanderbilt University Medical Center concluded infants born to women with opioid addiction also have a higher likelihood of dying in their first year of life.

Moreover, data published in 2024 indicated exposure to opioids during pregnancy increases an infant’s risk of suffering epilepsy, depressive disorders, attention deficit hyperactivity disorder (ADHD), mood disorders and other neuropsychiatric disorders.