Pregnant women are often told that acetaminophen (also called paracetamol) is one of the safest pain relievers to use when needed. While it remains an important medication during pregnancy, new research suggests scientists may need to better understand how prenatal exposure could affect the reproductive development of baby girls. The findings do not prove that paracetamol causes long-term problems, but they do highlight an area that deserves further study.
What Did the Study Look At?
Researchers followed 685 pregnant women in Denmark and examined 302 infant girls after birth. Mothers reported their paracetamol use every two weeks during pregnancy, and urine samples were also tested to measure paracetamol exposure.
The researchers then evaluated:
- Ovarian size
- The number of ovarian follicles, which contain immature eggs
- Reproductive hormone levels
- Uterine size
- Breast tissue development
The findings were also compared with a second, independent group of more than 1,200 girls who were followed from infancy into adolescence.
What Did the Researchers Find?
The study found that prenatal exposure to paracetamol was associated with several differences in reproductive development.
These included:
- Smaller ovaries in girls exposed early in pregnancy.
- Fewer ovarian follicles in girls exposed later in pregnancy.
- Smaller uterine size.
- Differences in reproductive hormone levels.
- Reduced breast tissue development during infancy.
The researchers also found that some of the differences in ovarian and uterine size were still present in the second group of girls followed into adolescence.
What Do These Findings Mean?
Ovarian follicles are small sacs inside the ovaries that contain immature eggs. Every female is born with a limited number of these follicles, making them an important part of future fertility.
The researchers believe the findings suggest that exposure to paracetamol during fetal development may influence how the ovaries and reproductive organs develop. However, the study did not determine whether these early differences lead to fertility problems or other reproductive health issues later in life.
Because this was an observational study, it cannot prove that paracetamol directly caused the changes that were seen. Other factors may also have contributed to the results.
Should Pregnant Women Stop Taking Acetaminophen?
No.
This study does not change current medical recommendations, and it does not show that pregnant women should avoid acetaminophenl altogether.
Paracetamol remains one of the most commonly recommended medications for treating pain and fever during pregnancy when it is medically needed. At the same time, researchers say these new findings support continuing to study how medicines may affect fetal development.
If you are pregnant:
- Do not stop prescribed medications without talking to your healthcare provider.
- Use paracetamol only when it is needed.
- Take the lowest effective dose for the shortest amount of time recommended by your healthcare provider.
- Talk with your obstetrician or midwife if you have questions about pain relief during pregnancy.
What This Means for You
This is the first human study designed specifically to examine whether prenatal acetaminophen exposure is associated with markers of ovarian development in infant girls. The findings suggest there may be a link, but they do not prove that acetaminophen causes reproductive problems or infertility.
More research, including long-term follow-up into adulthood, will be needed to determine whether these early differences have any lasting health effects. Until then, pregnant women should continue following their healthcare provider’s recommendations when using any medication during pregnancy.
Source
- Fischer MB, Kristensen DM, Juul A, Hagen CP, et al. Fetal exposure to paracetamol is associated with altered markers of ovarian development and reduced uterine volume in girls: the COPANA study. Hum Reprod Open. 2026;2026(3):hoag073. Accessed by: https://academic.oup.com/hropen/article/2026/3/hoag073/8787665?login=false.
