Can taking aspirin in pregnancy make your son infertile?

A study found the most vulnerable stage of pregnancy is four to six months when taking painkillers over a fortnight doubled the risk of have sons with testes problems

Pregnant women who take painkillers such as paracetamol, aspirin and ibuprofen could put their unborn sons at risk of fertility problems, researchers warn.

According to their findings, prolonged use of these common medicines may harm the development of boys’ sex organs.

Around half of women take over-the-counter painkillers during pregnancy, usually for headaches.

But using the drugs on their own or together may increase the risk of boys having undescended testicles, which can lead to poor sperm quality and testicular cancer in later life.

Women who used more than one type of painkiller simultaneously at any time while pregnant increased the risk seven-fold, on average.

But the most vulnerable stage is when a woman is between four and six months pregnant.

Then, taking one painkiller doubled the risk overall, when compared to women who took nothing. Paracetamol doubled the risk, while ibuprofen or aspirin increased it four-fold.

And using two painkillers together during this period increased the risk 16-fold, according to the study, published yesterday, in Europe’s leading reproductive medicine journal Human Reproduction.

Scientists believe the painkillers may be behind the increase in male reproductive disorders in recent decades, along with exposure in the womb to chemicals in the environment which are known as endocrine or hormone disruptors.

Dr Allan Pacey, of the University of Sheffield, said the findings were ‘somewhat alarming’.

‘I doubt that anyone would have suspected that common painkillers would have these effects.

‘It is worth noting the researchers found a significant difference when women had used painkillers for two weeks or more and that the impact was greatest when taking them during their second trimester,’ he said.

The study, by researchers from Denmark, Finland and France, looked at two groups of women who were questioned about their use of medication in pregnancy. The baby boys were examined at birth for any signs that the testes had failed to move into the scrotum before birth, ranging from mild to severe forms of the disorder.

The researchers found that the women in Denmark and Finland significantly under-reported the use of painkillers, especially paracetamol, thinking it was not medication.

Dr Henrik Leffers, senior scientist at Rigshospitalet in Copenhagen, who led the research, said mild painkillers acted as hormone disruptors, intensifying low-level exposure from environmental chemicals in the womb.

‘If exposure to endocrine disruptors is the mechanism behind the increasing reproductive problems among young men in the Western World, this research suggests that particular attention should be paid to the use of mild analgesics during pregnancy, as this could be a major reason for the problems.’

He added: ‘Women may want to try to reduce their analgesic use during pregnancy.’

Women are advised to avoid medicines where possible during pregnancy. Most manufacturers of ibuprofen and aspirin advise against it.

NHS advice to pregnant women needing short-term pain relief is to take paracetamol at the lowest dose for the shortest period.

Professor Richard Sharpe, of the Medical Research Council, said the second stage of pregnancy was the final stage of testes development, where disruption was most likely.

But he said: ‘It is important to say it was prolonged use of painkillers that had the biggest effect. Taking one or two painkillers occasionally for a headache is not going to affect the baby.’