Many pregnant women take paracetamol for pain or fever. It is one of the most common medicines used during pregnancy. A new study suggests a possible link between early pregnancy use and changes in the reproductive organs of infant girls.
The research found that girls exposed to paracetamol before birth had smaller ovaries and uterus in infancy. The effects were most clear with exposure in the first half of pregnancy. This has many parents asking what it means for their families.
Paracetamol is widely considered safe in pregnancy when used as directed. It is often the first choice for pain and fever. But animal studies have raised questions about how it might affect the developing fetus. This study adds human data to that conversation.
The old way of thinking focused mainly on short-term safety. The new research looks at subtle, long-term changes in organ development. It does not prove harm, but it suggests a need for caution.
Think of the developing ovary as a factory that builds a lifetime supply of eggs early on. Paracetamol might act like a switch that slows the assembly line. Fewer eggs are made, and the factory floor space, or ovarian volume, may be smaller.
The uterus is like a house that prepares for pregnancy later in life. If the house is built smaller during fetal development, it may stay smaller into infancy. This study measured that house size using ultrasound.
The study is called the Copenhagen Analgesic study, or COPANA. It followed healthy pregnant women in Denmark from early pregnancy through their infants’ first year. Researchers collected detailed reports of paracetamol use and measured urinary levels to confirm exposure.
In total, 685 women enrolled, and 302 girls were examined at follow-up. Girls were grouped by when they were exposed: early fetal life before 17 weeks, mid to late fetal life after 17 weeks, or not exposed at all. A small subgroup was exposed only in early fetal life.
Early fetal exposure was linked to smaller ovarian volume and uterine volume at infancy. Mid to late exposure was linked to fewer ovarian follicles, the tiny structures that hold eggs. Girls exposed only early had lower levels of a hormone called AMH, which reflects ovarian reserve.
Higher maternal urinary paracetamol levels were also tied to smaller breast tissue diameter in infancy. In a separate cohort of over 1,200 girls, fetal paracetamol exposure was linked to smaller uterine volume at puberty and smaller ovarian volume in adolescence.
This does not mean paracetamol is unsafe in pregnancy.
Experts note that animal studies show consistent effects on ovarian development. Human data like this study add weight, but they cannot prove cause and effect. The findings suggest a possible link, not a definite outcome.
What this means for you is straightforward. If you are pregnant or planning a pregnancy, talk with your doctor about any medicine use. Do not stop a prescribed treatment on your own. Ask about the lowest effective dose and the shortest duration needed.
The study has important limitations. It is observational, so it cannot prove paracetamol causes these changes. Researchers adjusted for fever and other factors, but some uncertainty remains. The study also focused on healthy, singleton pregnancies, so results may not apply to everyone.
What happens next is clear. More research is needed to confirm these findings and explore long-term effects. Scientists will look at larger groups and follow children into adolescence and adulthood. Until then, balanced guidance from your doctor is the best path forward.
