Paracetamol use in pregnancy 'may harm fertility of daughters'
The female offspring of rats given paracetamol when pregnant had smaller ovaries and smaller litters, scientists discovered
Mothers who take paracetamol during pregnancy could harm their future fertility of their daughters, a study suggests, Tests on animals found that when a mother was given paracetamol or the aspirin-like drug indomethacin, her female offspring had fewer eggs than those not exposed to the medicines.
The daughters also had smaller ovaries and gave birth to smaller litters of babies.
Males were affected too, having fewer cells that give rise to sperm later in life. However, their fertility recovered to normal levels by the time they matured into adults.
Despite the fact that foetal development is slower in humans than in rats, scientists say the findings are noteworthy given the ‘many similarities’ between the two species' reproductive systems.
Painkillers act on hormones called prostaglandins which are known to regulate ovulation, the menstrual cycle, and the induction of labour. The researchers warn that if the drugs are absolutely necessary, women should take the smallest possible dose.
Paracetamol is widely considered the only safe option for treating pain in pregnancy.
The drug has been routinely used during all stages of pregnancy to reduce a high temperature and for pain relief, with no definitive evidence to date that it has any harmful effects on the unborn baby.
NHS Choices recommends that women should avoid any drugs in pregnancy, particularly in the first three months.
But, if there is a need for painkillers, "paracetamol is usually safe to take", it says.
However, it advises that women should take the drug for the shortest amount of time possible at the lowest dose, and get advice from their midwife or GP.
Professor Richard Sharpe, from the University of Edinburgh's MRC Centre for Reproductive Health, who co-led the study published in the journal Scientific Reports, said: "It's important to remember that this study was conducted in rats, not humans. However, there are many similarities between the two reproductive systems.
"We now need to understand how these drugs affect a baby's reproductive development in the womb so that we can further understand their full effect."
Rats were given the drugs over several days and experienced effects after one to four days.
As well as affecting a mother's immediate offspring, the medicines also appeared to have an impact on subsequent generations.
Granddaughters of the animals given the painkillers while pregnant also had smaller ovaries and altered reproductive function.
Some painkillers may affect the development of "germ cells" that mature into eggs and sperm within the womb, the scientists believe.
Co-author Professor Richard Anderson, also from the University of Edinburgh, said: "These studies involved the use of painkillers over a relatively long period. We now need to explore whether a shorter dose would have a similar effect, and how this information can be usefully translated to human use."
Previous studies have suggested that paracetamol interferes with the reproductive systems of unborn children.
In May 2015, experts said using paracetamol in the long term could affect the reproductive health of baby boys.
University of Edinburgh scientists found that the painkiller interrupted the production of testosterone in baby mice when given for a week.
And in 2010, Danish researchers suggested the drug increased the risk of undescended testicles in male babies.
In 2014, American-led research said using paracetamol during pregnancy may raise the risk of children developing hyperactivity disorders.
The new research was funded by the Medical Research Council and the Wellcome Trust and published in the journal Scientific Reporters.