Mothers taking paracetamol during pregnancy could unwittingly be damaging the reproductive systems of their baby girls.
The painkiller may even have lasting effects on their granddaughters’ fertility.
Scientists have found that human ovaries exposed to paracetamol for a week in laboratories lost up to 40 per cent of their egg cells.
If this effect occurs in the womb, it could mean baby girls exposed to the common drug end up being born with fewer eggs. This would give them fewer years in which they could become pregnant and lead to an early menopause.
Mothers taking paracetamol during pregnancy could unwittingly be damaging the reproductive systems of their baby girls
Unborn boys could also be affected by the drug. But unlike women, whose egg supply is limited, they keep producing sperm throughout their lives, meaning the danger to their fertility is not as serious.
Paracetamol is the most widely used painkiller in the world and is the only one regarded as safe for pregnant women.
Previous studies have found that female rats and mice exposed to paracetamol in the womb have fewer eggs, smaller ovaries and go on to have fewer babies.
The previous research also found that the fertility of future generations of rats could be affected by a foetus being exposed to painkillers.
However, it is not yet known how this could affect humans. The latest research is the first to show the toll of analgesic drugs, including ibruprofen, on human foetal ovaries.
It also found that the drugs may affect the way reproductive systems function in future. The study prompts fresh warnings for pregnant women to only take paracetamol when necessary.
Human ovaries exposed to paracetamol for a week in laboratories lost up to 40 per cent of their egg cells, so baby girls exposed to the drug may end up being born with fewer eggs
Professor Richard Sharpe, one of the researchers from the University of Edinburgh, said: ‘This study identifies a potential risk from taking paracetamol or ibuprofen, although we don’t know exactly what effect it would have on human health nor what dose would be needed to harm fertility.’
He said the evidence that analgesic drugs interfere with production of sperm and egg cells is growing, adding: ‘We know the majority of women take analgesics in pregnancy for symptoms such as colds, headaches and fever.
‘There is a temptation, when paracetamol is there in the cupboard, to take it at the slightest sign of an ache or pain.’
Paracetamol is the most widely used painkiller in the world. Previous studies have found that female rats and mice exposed to paracetamol in the womb have fewer eggs
He said the NHS advises pregnant women to take the lowest dose of paracetamol for the shortest possible time.
The study, led by Dr Rod Mitchell from the University of Edinburgh and presented at the Fertility 2018 conference in Liverpool, tested the effect of paracetamol and ibuprofen on human foetal testes and ovaries over a week. Researchers counted germ cells that turn into sperm and eggs.
In the ovary, the number of egg cells fell by up to 40 per cent, while in testes the number of germ cells was reduced by more than a fifth.
Paracetamol and ibuprofen are believed to interfere with a hormone called prostaglandin E2, which appears to play a vital part in the development of the foetal reproductive system.