MRI Finds Smaller Brains in Opioid-Exposed Fetuses

Third-trimester fetuses exposed to opioids in utero have multiple smaller 2D biometric measurements of the brain altered fetal physiology on investigational MR, according to a study in the American Journal of Roentgenology (AJR).

Noting the scarcity of imaging literature evaluating prenatal opioid exposure on brain development, “our findings demonstrate the impact of prenatal opioid exposure on fetal brain development, which may in turn affect postnatal clinical outcomes,” wrote first author Usha D. Nagaraj, MD, from Cincinnati Children’s Hospital Medical Center in Ohio.

Nagaraj and colleagues’ prospective multicenter case-control study included 65 women (mean age, 29 years) in their third trimester of pregnancy who underwent fetal MRI from July 1, 2020 through December 31, 2021 at three US academic medical centers: Cincinnati Children’s Hospital Medical Center, Arkansas Children’s Hospital, and the University of North Carolina at Chapel Hill. A total of 28 fetuses (mean gestational age, 32.3 weeks) were classified as opioid-exposed, while 37 fetuses (mean gestational age, 31.9 weeks) were unexposed in utero.

Fourteen 2D biometric measurements of the fetal brain were manually assessed and used to derive four indices.

When adjusting for gestational age, fetal sex, and nicotine exposure, 7 of the 14 2D biometric measurements—cerebral fronto-occipital diameter, bone biparietal diameter, brain biparietal diameter, corpus callosum length, vermis height, anterior-posterior pons measurement, and transverse cerebellar diameter—were significantly smaller in opioid-exposed fetuses than in unexposed fetuses, as measured on fetal MRI.

“In addition,” the authors of this AJR article concluded, “fetuses with prenatal opioid exposure had increased frequencies of breech presentation and of increased amniotic fluid volume.”