Beware: taking paracetamol while pregnant could harm the fertility of one’s future daughters, a new study suggested.

When a mother rat was given painkillers while pregnant, her female offspring had smaller ovaries, fewer eggs, and smaller babies than those who were not exposed to the medications. Even male offspring were affected at birth and exhibited smaller counts of germ cells (which become sperm later on), although their reproduction bounced back during adulthood.

Study co-lead author and professor Richard Sharpe of University of Edinburgh said the results indicated that painkillers should be used cautiously during pregnancy.

"It's important to remember that this study was conducted in rats not humans, however, there are many similarities between the two reproductive systems,” Sharpe said in a statement, recommending that pregnant women adhere to current painkiller use guidelines at the lowest dose for the shortest time possible.

In the study, the team gave pregnant rats two painkillers: paracetamol and indomethacin, a prescription painkiller belonging to the same class as aspirin and ibuprofen.

They saw the drugs’ effects one to four days from start of treatment – although it should be noted that fetal development is much slower in humans than in rats.

Apart from the results in offspring, the painkillers also affected other generations, with the granddaughters having decreased ovary size and altered reproductive function.

Likely causing these effects is the way painkillers act on prostaglandins, which are hormones known to regulate ovulation, menstruation, and labor induction.

Previous research suggested paracetamol’s effect on baby boys’ reproductive health. A University of Edinburgh-led study, for instance, found that the drug may reduce the production of testosterone in the unborn male child, likely increasing the risk for testosterone cancer and infertility.

Paracetamol is widely deemed as a safe choice for the treatment of pain during pregnancy. It has been used routinely during all pregnancy stages to manage pain and high temperature.

The UK’s National Health Service, for instance, recommends that if there is any need for painkillers, paracetamol “is usually safe to take.” It urges avoiding any other drugs during pregnancy, especially in the first quarter.

The findings were published in the journal Scientific Reports.

Photo: Ambrose Heron | Flickr

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