A Korean Study Links Opioids in Pregnancy to More Hospital Stays for Children

A nationwide South Korean birth cohort, published Oct. 13, 2026, in PLOS Medicine, reports that children whose mothers were prescribed opioids during pregnancy were later admitted to the hospital 28% more often than children with no such exposure. The study links prescribing to admissions; it does not show that the medicines caused them.

The authors of the PLOS Medicine paper say the result may inform postnatal monitoring and care for children born to mothers who received opioids in pregnancy. They also write that opioids should be used in pregnancy when the expected benefits clearly outweigh the risks, and that avoiding them is not always feasible.

The team used South Korea's national health insurance records, linking mothers to 2,928,186 children born between 2010 and 2017 and following them to the end of 2023. A child was counted as exposed if the mother received two or more opioid prescriptions in a single trimester. The authors note that such records show what was prescribed, not what was taken.

Admission rates rose with the dose prescribed and with how long it was prescribed. Higher rates appeared across infections, breathing and digestive illnesses, dental and urinary conditions and injuries. The gap narrowed as children grew and was no longer evident past five years of age.

The paper runs the comparison again between siblings, setting a child against a brother or sister with no such exposure, which cancels out much of what a family shares. There the gap fell to 8% and remained statistically significant. The authors read that drop as a sign that shared family factors explain part of the association, and they say confounding they could not measure cannot be ruled out.

Hyeon Jin Kim and Yesol Yim of Kyung Hee University College of Medicine in Seoul are joint first authors, with Dong Keon Yon and colleagues. The study protocol and the analysis code are public on GitHub and archived in Zenodo; the insurance records themselves must be requested from the agency. South Korean government ministries funded the work and had no role in its analysis or publication.