Now paracetamol on scare list
Women who take paracetamol during pregnancy could harm the fertility of their unborn daughters, a study suggests,
Tests on female rats found that those given paracetamol or the aspirin-like drug indomethacin produced female offspring with fewer eggs than those not exposed to the medicines. The female offspring also had smaller ovaries and gave birth to smaller litters.
Infant male rats were affected too, having fewer of the cells that produce sperm in later life. However, their fertility was normal by the time they had matured into adults.
Painkillers act on hormones called prostaglandins, which are known to regulate ovulation, the menstrual cycle and the induction of labour.
The researchers say pregnant women should avoid paracetamol and indomethacin, and, if they must be taken, the smallest dose should be used.
Paracetamol has long been considered the only safe option for treating pain in pregnancy.
The drug has been routinely used during all stages of pregnancy to reduce temperature and for pain relief, and there has been no firm evidence that it has harmful effects on foetuses.
Professor Richard Sharpe, of Edinburgh University's MRC Centre for Reproductive Health, and joint leader of the study published in the journal Scientific Reports, said: "It's important to remember that this study used 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 understand their full effect [in later life]."
As well as affecting a female's immediate offspring, the medicines 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 might affect the development in foetuses of the germ cells that mature into eggs or sperm, the scientists believe.
The co-author of the report, Professor Richard Anderson, also of Edinburgh University, said: "These studies involved the use of painkillers over a relatively long period. We now need to explore whether a shorter dose period would have a similar effect, and how this information can be translated to human use."
Previous studies have suggested that paracetamol interferes with the reproductive systems of unborn children. In May 2015, experts said long-term use of paracetamol could affect the reproductive health of boys.
Edinburgh University scientists found the painkiller interrupted production of testosterone in baby mice when given for a week.
In 2010, Danish researchers suggested that the drug increased the risk of undescended testicles in male babies.
In 2014, US-led research said using paracetamol during pregnancy might raise the risk of hyperactivity disorders developing in children.