Scientists tracking children's development from infancy into adolescence noticed a surprising trend among some girls in their study. The clue pointed back to something their mothers had taken during pregnancy. Researchers in Denmark found that girls exposed to paracetamol (Tylenol) in the womb showed differences in several markers linked to ovarian development, from infancy through adolescence.
The study, published in *Human Reproduction Open*, followed 302 girls from a prospective Danish pregnancy cohort and examined markers of reproductive development during infancy. Researchers tracked mothers' paracetamol use throughout pregnancy using detailed questionnaires and urine samples. The team found that daughters exposed to paracetamol during pregnancy tended to have smaller ovaries and uteruses, along with differences in ovarian activity. Girls exposed during early pregnancy had reduced ovarian volume and smaller uterine volume compared with unexposed children, while exposure later in pregnancy was associated with fewer ovarian follicles, the structures that contain immature eggs.
Researchers also observed lower levels of anti-Müllerian hormone (AMH) among some girls exposed early in pregnancy. In adults, AMH is often used as a marker of ovarian reserve, though the significance of differences seen in infancy is not yet clear. To confirm persistence, the researchers examined an independent cohort of 1,210 girls followed from infancy into adolescence. There, they found similar patterns: prenatal exposure to paracetamol was associated with smaller uterine volume at puberty and reduced ovarian volume during adolescence.
Lead author Dr. Margit Bistrup Fischer emphasized that while the findings do not prove the drug caused the changes, they add to growing evidence from animal studies that fetal exposure may have lasting effects on female reproductive health. She stressed that pregnant women should not stop taking paracetamol if needed but noted it contributes to a growing signal to consider its use more carefully. Dr. Lucy Hooper, an independent general practitioner, pointed out that the study measured markers like ovarian size and hormone levels but not long-term reproductive outcomes, cautioning that the findings should be interpreted with care, as some differences were small and not precisely measured.
The study suggests potential long-term effects on ovarian function but does not yet determine whether these changes impact fertility. Dr. Fischer concluded that while the evidence is not yet strong enough to change medical guidelines, it may prompt closer consideration of paracetamol use during pregnancy.
Source: Newsweek
