Infertility link to paracetamol - painkillers during pregnancy can harm boys

Current guidelines issued by the Department of Health say women are able to take mild analgesics such as paracetamol and ibuprofen without any danger to their unborn children.

But according to the new work, ibuprofen and aspirin quadruple the risk of a baby being born with a condition affecting semen production, if taken in the fourth, fifth and sixth months of pregnancy.

A doubling of the risk was found for paracetamol. But taking more than one painkiller at the same time increased the risk 16-fold.

Taking the drugs could lead to women giving birth to sons with undescended testicles (cryptorchidism) — a condition known to be a risk factor for poor semen quality. It is also said to increase the risk of testicular germ cell cancer.

Fertility expert Dr Allan Pacey at the University of Sheffield this afternoon said the findings were "alarming" and called for more research "as a matter of priority".

The study in the journal Human Reproduction supported findings in another study which showed painkillers disrupted androgen (steroid hormone) production, leading to insufficient supplies of testosterone during the crucial early period of gestation when the male organs were forming. Dr Henrik Leffers, senior scientist at Rigshospitalet in Copenhagen, said his 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".

The study looked at two groups of women, 834 in Denmark and 1,463 in Finland. In Finland the women answered written questionnaires about their use of medication during pregnancy and in Denmark the women did the same or took part in a phone interview, or both. The phone interview asked specifically about the use of painkillers during pregnancy, while the written questionnaires did not. The baby boys were examined at birth for any signs of cryptorchidism.

Among the Danish mothers 31 per cent reported using painkillers in the questionnaire, but 57 per cent reported it in the telephone interview. Of these, a significant number of their baby boys showed signs of the condition.

Among the Finnish women, there were no such significant findings but researchers believe this is due to women under-reporting because they did not consider mild painkillers to be "medication".

A government publication, The Pregnancy Book, updated in June, advised some painkillers are "safe", but says pregnant women should check before taking any medicine.