The use of painkillers including paracetamol, aspirin and ibuprofen in pregnancy could be linked to male reproductive disorders, a new study shows.

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The scientists behind a new study believe that there is a link between the use of painkillers and women giving birth to babies with undescended testicles - a condition which is linked to fertility problems later in life, and an increased risk of testicular cancer.

The study, published in the journal Human Reproduction, suggested that women who take more than one painkiller at the same time while pregnant, or during the second trimester, are particularly likely to give birth to boys with the condition, known as cryptorchidism.

More than half of all pregnant women in the UK, Europe and United States take painkillers while pregnant. The study's authors urged caution in overstating the risks of the painkillers while pregnant, and called for more urgent research, but said the link may be part of the reason for the increase in male fertility disorders of recent years, possibly by interfering with testosterone.

We recommend that pregnant women seek advice from their physician before using mild analgesics and in general follow the advice to use as little medicine during pregnancy as possible. Lead scientist Dr Henrik Leffers.

Lead scientist Dr Henrik Leffers, from Copenhagen University Hospital, said: "We recommend that pregnant women seek advice from their physician before using mild analgesics and in general follow the advice to use as little medicine during pregnancy as possible."

Current advice from the NHS is for women to avoid taking medicines while pregnant, but paracetamol is seen as acceptable in small doses. Ibuprofen and aspirin are only recommended under certain conditions.

Using painkillers while pregnant could damage the fertility of male children, a study suggests (Reuters).

Potential link

Women who used more than one painkiller at the same time were seven times more likely to give birth to son with some form of undescended testicles. Between the third and sixth month of pregnancy, any use of analgesics doubled the risk of the condition. Women who took the drugs for more than a two-week period were found to have the highest risk.

The study, based on telephone interviews and examinations in Denmark and Finland, backs up evidence from a study on rats, which found that analgesics disrupted androgen production, leading to insufficient testosterone production during the early part of pregnancy. The drugs reduced the testosterone in the testes of the male rats by 50 per cent.

The experts said the painkillers could act as endocrine disruptors - chemicals which disrupt hormone balance.

Dr Leffers said: "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."

Male fertility problems

The study authors said the condition of undescended testicles had risen dramatically in recent years, for example in Denmark, where it rose from 1.8 per cent of the population affected in 1959/1961 to 8.5 per cent in 1997/2001.

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. Dr Leffers.

Dr Leffers added: "Although we should be cautious about any over-extrapolation or over-statement, the use of mild analgesics constitutes by far the largest exposure to endocrine disrupters among pregnant women, and use of these compounds is, at present, the best suggestion for an exposure that can affect a large proportion of the human population.

"A single paracetamol tablet (500mg) contains more endocrine disrupter potency than the combined exposure to the 10 most prevalent of the currently known environmental endocrine disruptors during the whole pregnancy.

"In fact, a single tablet will, for most women, be at least a doubling of the exposure to the known endocrine disruptors during the pregnancy and that dose comes on a single day, not spread out over nine months as with the environmental endocrine disruptors. Thus, for women using mild analgesics during the pregnancy, the mild analgesics will be by far the largest exposure to endocrine disruptors."