Tylenol Use in Pregnancy May Reduce Daughters’ Fertility, Study Finds

Female ​reproductive organ development could be impacted by a mother taking Tylenol—also known as acetaminophen or paracetamol—during pregnancy, according to researchers in Denmark.

Long-term follow-up will be required to determine whether the differences observed in infants have implications for fertility later in life and a woman’s age at menopause, study leader Margit Bistrup Fischer of Rigshospitalet in Copenhagen said in a statement accompanying the study.

Animal studies have ​previously suggested that fetal exposure to Tylenol, the most commonly used drug in pregnancy, might affect ovarian egg reserve and later reproductive function, but this is the first time that research has reported similar findings in humans.

Women ‘Should Not Be Alarmed’

Women who have used Tylenol, the brand name for the generic drug acetaminophen, widely known as paracetamol outside of North America, during ​pregnancy should not be alarmed, Fischer said.

“Animal studies have demonstrated that impaired formation of ovarian follicles can lead to reduced fertility and earlier reproductive aging. 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.

“Women who have used paracetamol during pregnancy should not be alarmed by our findings. Our study examined associations at the population level and cannot predict outcomes for any individual woman or child,” she said.

The researchers studied 302 3-month-old girls whose mothers’ use of Tylenol had been tracked during pregnancy. Of these babies, 92 were first ⁠exposed to the drug in the womb before 17 weeks of pregnancy, 67 were exposed after 17 weeks, and 143 were born to mothers who ​had not used the drug while pregnant.

The women all took relatively low amounts, with ​none exceeding the recommended daily maximum dose of 4,000 milligrams. Most took it to help with headaches or musculoskeletal pain.

A girl’s ovarian reserves are established while she is a developing baby in the womb, although other factors may determine the age she goes through puberty and menopause.

The 3-month-old girls in the study who were exposed to Tylenol in utero had ovaries that were 40 percent smaller, wombs that were on average 13 percent smaller, and 23 percent fewer ovarian follicles, the researchers found.

Babies exposed early in pregnancy—before 17 ​weeks—also had lower levels of ​Anti-Müllerian hormone, an indicator of the ⁠number and quality of eggs in the ovaries.

Smaller Wombs and Ovaries

The researchers also followed a separate group of 1,210 girls from infancy to adolescence whose mothers had reported Tylenol use during pregnancy. Fetal ​exposure in this group was associated with smaller uteruses at puberty and smaller ovaries during adolescence.

The study cannot predict outcomes for ​any individual female, Fischer said, explaining that many women who used Tylenol during pregnancy had daughters whose ovarian measurements were similar to those of daughters born to women who did not use the drug.

Current guidelines from health authorities recommend Tylenol as safe for treating pain and fever during pregnancy. Untreated high fever or severe pain can themselves ⁠pose risks ​to both mother and baby, Fischer said.

Dr. Christian De Geyter, ​a reproductive medicine specialist at the University Hospital of Basel, Switzerland, said in an accompanying commentary that the findings of the study fit well with data from animal research, and that their importance “cannot be stressed enough.”

Follow-up of girls in the study should ​extend into menopause, he said, adding that recommendations on the drug’s use during pregnancy should be reconsidered.

Franziska Denk, professor of neuroscience at King’s College London, said the study was “good quality research,” although he thought the sample size was too small for the 13 different variables being examined.

“Right now, I think it is too early to recommend a change in behavior—as correctly indicated by the authors in the press release,” he said.

‘Several Notable Weaknesses’

Stephen Burgess, professor of biostatistics at the University of Cambridge, said the study had “several notable weaknesses.”

“Mothers who took paracetamol during pregnancy are likely to differ substantially from those that did not—this is known as confounding. Confounding makes it difficult to know whether differences between outcomes are attributable to paracetamol itself or to other characteristics of the mothers or their pregnancies,” he said.

He said that it could not be determined that the drug was the cause of the differences found by the researchers.

“It may be that these findings are driven by infection or fever—women take paracetamol due to mild sickness, and this sickness is the cause of differences in early-life ovarian volume. It may be that impaired fetal development and its causes are what lead to increased paracetamol usage, not that increased paracetamol usage leads to impaired fetal development.”

Burgess added that even if there were negative consequences of taking paracetamol during pregnancy, there were “likely future negative consequences attributable to taking away one of the only remaining available and widely tolerated medications from pregnant women.”

US Officials Linked Drug to Autism

Health and Human Services (HHS) Secretary Robert Kennedy Jr. and Trump spoke about the use of Tylenol during pregnancy in September 2025, with the government subsequently advocating caution over prenatal exposure. The department’s current fact sheet says exposure to the drug during pregnancy is an unresolved area of concern, while acknowledging that causality has not been established.

The Food and Drug Administration (FDA) continues to monitor and evaluate the drug’s use in pregnancy, but states that it has not found clear evidence that Tylenol’s use at recommended safe levels causes adverse pregnancy, birth, neurobehavioral, or developmental outcomes.

The FDA and HHS did not immediately respond to requests for comment on the Danish study.

The American College of Obstetricians and Gynecologists (ACOG) told The Epoch Times in an emailed statement that the clinical significance of the study’s findings remain “uncertain or unknown,” and that current guidelines for women should not change because of it.

“The oldest participants evaluated were adolescents, and the study cannot determine whether the observed differences are associated with future reproductive outcomes such as fertility, ovulatory function, reproductive lifespan, or other measures of reproductive health,” it said, adding that the observational study had various limitations.

“These findings should be viewed as a potential area for further investigation and do not indicate that current clinical recommendations should change. Consistent with ACOG’s existing guidance, acetaminophen remains one of the only safe medications that can be used during pregnancy when indicated, and patients should consult their obstetric care professional before making any changes to medication use.”

Ongoing Lawsuit

The Danish findings come as Tylenol manufacturers face an ongoing lawsuit in the United States over alleged risks associated with prenatal exposure.

Texas Attorney General Ken Paxton has sued Kenvue, which now owns the Tylenol brand after Johnson & Johnson spun off its consumer health business into a new company in 2023. The suit alleged that the company engaged in deceptive advertising by failing to disclose evidence concerning a possible link between prenatal Tylenol exposure and autism.

While a judge dismissed most of the claims, one consumer-protection claim against Kenvue Brands LLC has been allowed to proceed, with the company’s attempt to have it dismissed rejected in February.

In an emailed statement to Reuters, Kenvue advised pregnant or breastfeeding women ⁠to check with a health professional before using acetaminophen, which the company says is the most studied and safest pain reliever during pregnancy.

It noted that the study has methodology limitations and ​does not support a causal relationship between the drug and postnatal reproductive development.

Kenvue shares fell more than 3 percent Wednesday following the study’s publication.