Women who use painkillers such as aspirin, ibuprofen and paracetamol during pregnancy run the risk of giving birth to baby boys with reproductive disorders, a study has suggested.
Research found that women who take more than one painkiller at the same time during pregnancy, or who take the drugs during the second trimester, have an increased chance of having a child with undescended testicles - a condition that affects around one in 20 boys in the UK.
Testicular cancer is more prominent in men who have the condition, known as cryptorchidism, which is also linked to fertility problems later in life.
Scientists behind the research say the use of painkillers could have contributed in part to a rise in male reproductive disorders in recent decades, possibly by interfering with the role of the male hormone testosterone. More than half of pregnant women in Europe and the US report taking mild painkillers.
The NHS advises that women should avoid taking medicines during pregnancy but the use of paracetamol is considered safe if taken in small doses for short-term pain relief.
Pregnant women are not recommended to take ibuprofen because of possible risks to the child, apart from during weeks 14 to 27 when it is considered to be safe.
Women at risk of the pregnancy condition pre-eclampsia can be advised by doctors to take small doses of aspirin, although it is not generally recommended.
In the latest study, published in the journal Human Reproduction, experts from Denmark, Finland and France quizzed women on their use of the drugs during pregnancy.
Some 1,463 women in Finland completed written questionnaires and another 834 women in Denmark filled in the same questionnaire, took part in a telephone interview, or did both.
The results showed that women who used more than one painkiller simultaneously (such as paracetamol and ibuprofen) were seven times more likely to give birth to sons with some form of undescended testes compared with women who did not take the drugs.