TUESDAY, Sept. 15, 2026 (HealthDay News) — Exposure to acetaminophen in the womb may be linked to differences in how a girl's reproductive system develops.

Acetaminophen — the active ingredient in Tylenol — is commonly used to treat pain and fever during pregnancy.

Researchers in Denmark examined 302 baby girls at about 3 months of age.

Those exposed to acetaminophen before birth had, on average, smaller ovaries and uteruses as well as fewer ovarian follicles — the structures that contain immature eggs.

Girls exposed exclusively in early fetal life also had lower levels of a hormone used as a marker of ovarian egg reserve.

A separate group that was followed longer showed similar differences: smaller uteruses at puberty and smaller ovaries during adolescence.

The study was observational and does not prove acetaminophen caused the differences, but researchers said their findings were consistent with previous animal studies.

The lead author stressed that women who used acetaminophen during pregnancy should not be alarmed, and the findings should not dissaude women from using it when medically needed.

"Whether the differences observed in our study have implications for fertility and age at menopause in humans remains unknown and will require long-term follow-up of the girls in our cohort," said lead author Dr. Margit Bistrup Fischer of the Department of Growth and Reproduction at the Rigshospitalet in Copenhagen.

The advice for now: Decisions about pain management during pregnancy should be made with a healthcare professional.

The findings were published recently in the journal Human Reproduction Open.

More information

The American College of Obstetricians & Gynecologists has more on the use of acetaminophen in pregnancy.

SOURCE: HealthDay TV, Sept. 15, 2026