Tylenol During Pregnancy May Be Linked to Changes in Baby Girls' Ovaries and Uterus, Study Finds

Taking Tylenol during pregnancy may be associated with differences in baby girls' reproductive organs, according to a recent study.

Researchers found that girls exposed to paracetamol during foetal development had smaller ovaries and uteruses, as well as fewer ovarian follicles, than girls who were not exposed.

However, the findings do not show that Tylenol causes these changes or that girls exposed before birth will experience fertility problems later in life.

The study, published in Human Reproduction Open, examined 302 three-month-old girls whose mothers' paracetamol use was monitored during pregnancy. Researchers also looked at an independent group of 1,210 girls who were followed from infancy into adolescence.

Does This Mean Tylenol Can Affect Future Fertility?

The study examined differences in reproductive organs and biological markers. It did not assess whether the girls later experienced infertility, early menopause, or other reproductive issues.

That distinction is significant because the research was observational. Researchers found an association between prenatal paracetamol exposure and certain reproductive measurements, but they cannot prove that the medication caused these differences.

Other factors may also be involved. The researchers acknowledged that residual confounding, including why a mother took paracetamol in the first place, could not be completely eliminated. For example, women may have taken the medication because they were experiencing pain or fever, which could itself affect pregnancy outcomes.

The study also cannot predict what will happen to any specific child as growth and upbringing can be affected by many different factors as life progresses.

Lead researcher Margit Bistrup Fischer said women who used paracetamol during pregnancy should not be alarmed by the findings. She also stressed that the study does not establish whether the observed differences will have any long-term consequences for reproductive health.

Why are Researchers Paying Attention to this?

The reproductive system begins developing before birth, making foetal exposure to medications an important area of study.

Previous animal studies have suggested that prenatal paracetamol exposure may affect the development of ovarian follicles and later reproductive function. The new study is notable because it examined similar reproductive markers in humans.

However, researchers stressed that the clinical significance of the differences they observed remained unknown. In other words, it is not yet clear whether smaller ovaries or uteruses, or differences in ovarian follicles, would translate into any meaningful health effects later in life.

The study's authors said longer term research is needed to determine whether these early differences have any consequences for reproductive health, including reproductive lifespan and the timing of menopause.

Should Pregnant Women Stop Taking Tylenol?

The study does not provide sufficient evidence to conclude that pregnant women should stop taking paracetamol.

Current guidelines continue to include paracetamol, also known as acetaminophen, as an option for treating pain and fever during pregnancy. Researchers also note that untreated high fever or severe pain can pose risks during pregnancy.

The main takeaway is that the study raises new questions rather than providing a definitive answer about Tylenol's safety during pregnancy.

More research, particularly studies that follow children into adulthood, is needed to determine whether the reproductive differences observed in the study have any significant impact on fertility or reproductive health later in life.