A recent study has suggested that exposure to Tylenol, also known as acetaminophen, during pregnancy may be associated with certain changes in the reproductive systems of female infants. Researchers examined 302 three-month-old girls, tracking their mothers’ use of Tylenol throughout pregnancy. The study grouped the infants based on when their mothers first used the drug during pregnancy: 92 were exposed before 17 weeks, 67 after 17 weeks, and 143 were not exposed at all. Researchers measured Tylenol levels using urine samples from the mothers, who generally used the medication in small amounts, mostly for headaches or muscle pain, without exceeding the recommended daily limit of 4,000 milligrams. The study found that infants exposed to Tylenol in the womb had smaller ovaries, fewer ovarian follicles—structures that hold immature eggs—smaller uteruses, and lower levels of reproductive hormones. Those exposed earlier in pregnancy, before 17 weeks, had lower levels of Anti-Müllerian hormone, which is an indicator of egg quantity and quality. The researchers also looked at a larger group of 1,210 girls who were followed from infancy into adolescence. In this group, prenatal Tylenol exposure was linked to smaller uteruses at puberty and smaller ovaries during adolescence. The study’s lead author, Margit Bistrup Fischer from Rigshospitalet in Copenhagen, emphasized that the findings do not prove Tylenol caused these changes or affect future fertility. She urged pregnant women not to be alarmed by the results, noting that many girls exposed to the drug had reproductive organs of normal size. Fischer also pointed out that the study cannot predict individual outcomes. Medical guidelines still consider Tylenol a safe choice for treating pain and fever during pregnancy. Fischer noted that untreated severe pain or high fever can pose risks to both mother and fetus. In a related commentary, Dr. Christian De Geyter, a reproductive medicine specialist, said the findings align with previous animal studies. He recommended continuing to monitor girls exposed to Tylenol in utero throughout their lives, including into menopause, and suggested that current recommendations on Tylenol use during pregnancy might need reevaluation. Previous research had hinted that Tylenol exposure during pregnancy could affect egg reserves and reproductive health, but this is the first study to report such findings in humans. President Donald Trump once claimed a link between Tylenol use during pregnancy and autism, but this claim has been widely dismissed by medical experts as lacking scientific support.