In a new study published in Human Reproduction Open, scientists reported that infants whose mothers took acetaminophen (commonly known as Tylenol) while pregnant showed measurable differences in reproductive organ development. The research, led by Dr. Margit Bistrup Fischer of Rigshospitalet in Copenhagen, examined 302 three‑month‑old baby girls and compared those whose mothers used the medication with those who did not.
Key findings
Among the infants exposed to acetaminophen in utero, the average ovarian volume was about 40% smaller, uterine volume roughly 13% smaller, and the number of ovarian follicles 23% lower than in the unexposed group. Girls whose mothers began taking the drug before 17 weeks of pregnancy also had reduced levels of anti‑Müllerian hormone, a marker of egg quantity and quality.
Researchers also looked at a separate cohort of 1,210 girls followed from infancy through adolescence. In that group, prenatal acetaminophen exposure was associated with smaller uterine size at puberty and reduced ovarian size during teenage years.
Study limitations and context
Dr. Fischer emphasized that the study does not establish that acetaminophen causes the observed changes, nor does it predict future fertility or menopause timing for any individual. Many women who used the medication during pregnancy gave birth to daughters whose reproductive measurements matched those of unexposed peers.
The mothers in the study reported relatively low daily doses, never exceeding the recommended maximum of 4,000 mg, and most used the drug for common headaches or musculoskeletal pain. Current medical guidelines continue to list acetaminophen as safe for treating pain and fever during pregnancy, noting that untreated high fever or severe pain can pose greater risks to both mother and fetus.
Expert commentary
Dr. Christian De Geyter, a reproductive‑medicine specialist at the University Hospital of Basel, said the human findings align with animal research that has suggested potential impacts on ovarian reserve. He called for longer‑term follow‑up into menopause to fully understand any lasting effects and suggested that recommendations on acetaminophen use during pregnancy may need to be revisited.
Political backdrop
President Trump has previously linked acetaminophen use in pregnancy to autism, a claim that the broader medical community and major health organizations have dismissed as lacking scientific support. The study’s authors did not find evidence of a link to autism, and they stressed that their data do not support the President’s assertion.
For expectant mothers, the takeaway remains balanced: acetaminophen remains the most widely used pain reliever in pregnancy, and its short‑term benefits for managing fever and pain are still considered important. Women should discuss any medication concerns with their healthcare providers and weigh the risks and benefits on an individual basis.
What’s next?
The research team plans to continue monitoring the study participants into adulthood to assess any long‑term reproductive outcomes. Until more definitive data are available, clinicians are likely to maintain current prescribing practices while staying alert to emerging evidence.
Original reporting: Appleton, WI News Feed (HLL/CB) — read the source article.
