Tylenol Use in Pregnancy Linked to Daughter’s Uterus and Ovary Changes

Infant Ovarian and Uterine Measurements After Prenatal Exposure

Researchers examined 302 three-month-old baby girls to assess the relationship between prenatal acetaminophen exposure and early reproductive development. According to the study, urine samples collected at regular intervals tracked the mothers’ medication use during pregnancy. Within the entire cohort, 92 babies encountered prenatal exposure prior to the 17th week of gestation, 67 experienced their initial exposure after 17 weeks, and 143 were born to women who abstained from the medication. None of the mothers exceeded the recommended daily maximum dose of 4,000 milligrams, and most took the medication for headaches or musculoskeletal pain.

Infants exposed in utero showed significant anatomical differences compared to unexposed peers. Based on the measurements recorded, the exposed babies presented a 40% reduction in average ovarian volume, a 13% decrease in average uterine volume, and a 23% drop in the count of ovarian follicles—the structures containing immature eggs. Furthermore, babies exposed early in pregnancy before 17 weeks displayed lower levels of Anti-Müllerian hormone, which serves as an indicator of egg quantity and quality.

Adolescent Follow-Up Data and Individual Variability

To understand whether these early anatomical variations persist, researchers analyzed a separate cohort of 1,210 girls followed from infancy to adolescence whose mothers reported Tylenol use during pregnancy. According to the report, fetal exposure in this older group associated with smaller uteruses at puberty and smaller ovaries during adolescence. However, Fischer noted that the study cannot predict outcomes for any individual child, as many women who used Tylenol during pregnancy had daughters with ovarian measurements comparable to those of unexposed mothers.

Long-term follow-up will be necessary to determine whether these differences impact fertility later in life or the age at menopause, Fischer stated. Animal studies previously suggested that fetal exposure to acetaminophen might affect ovarian egg reserve and later reproductive function, but Dr. Christian De Geyter, a reproductive medicine specialist at the University Hospital of Basel in Switzerland, noted in an accompanying commentary that this study marks the first time similar findings have been reported in humans.

Medical Guidelines and Safety Reassurances

Despite the new anatomical data, major health authorities and study authors stress that women should not be alarmed. Current medical guidelines continue to recommend Tylenol as safe for treating pain and fever during pregnancy. Fischer pointed out that untreated high fever or severe pain can pose direct risks to both the mother and the developing fetus. Similarly, a study published in JAMA Pediatrics on April 14, examining 1.5 million children born from 1997 to 2022, found no link between prenatal Tylenol use and autism risk, successfully dispelling prior claims made by the Trump administration.

Frequently Asked Questions

Does taking Tylenol during pregnancy cause infertility?

According to study leader Margit Bistrup Fischer, the study does not indicate any effect on the girls’ future fertility, and determining whether these anatomical differences have long-term implications requires extended follow-up.

Is Tylenol still considered safe to use for pain and fever during pregnancy?

Yes. Current guidelines continue to recommend acetaminophen as a safe option for treating pain and fever, as leaving high fevers or severe pain untreated can pose risks to both mother and fetus.

Have studies linked prenatal Tylenol use to autism?

No. A study published in JAMA Pediatrics found no association between Tylenol use during pregnancy and autism, concluding that previous claims lacked robust scientific backing.