Danish Study Links Prenatal Acetaminophen Exposure to Altered Reproductive Development in Girls, Urging Caution Without Alarm

A prospective observational study from Denmark's COPANA cohort, published in Human Reproduction Open, has found associations between maternal paracetamol (acetaminophen/Tylenol) use during pregnancy and smaller ovarian and uterine volumes, fewer ovarian follicles, and lower Anti-Müllerian hormone levels in infant daughters at three months of age. Led by Dr. Margit Bistrup Fischer at Rigshospitalet in Copenhagen, the research examined 302 girls whose mothers reported use tracked via questionnaires and urinary biomarkers; exposed infants showed approximately 40% smaller ovarian volume, 13% smaller uterine volume, and 23% fewer follicles on average compared to unexposed peers. Early exposure (before 17 weeks) correlated with reduced ovarian/uterine size and lower AMH, while later exposure linked more to follicle count. A confirmatory analysis of 1,210 girls from an earlier Copenhagen cohort extended findings to smaller ovaries in adolescence and uteruses at puberty. These markers align with prior animal models suggesting impacts on ovarian reserve, though the study is observational and does not establish causation; long-term fertility or menopause timing effects remain unknown and require follow-up. Experts emphasize paracetamol remains the preferred analgesic for pain or fever in pregnancy due to risks of untreated symptoms, with guidelines unchanged. At a population level, if associations hold, this could contribute to subtle shifts in reproductive timelines amid already declining fertility trends, highlighting the need for refined risk-benefit discussions in prenatal care and further mechanistic research into endocrine disruption. Women are advised against alarm, as individual outcomes vary widely and many exposed daughters showed normal measures.