Painkillers in pregnancy may affect offspring's fertility

Taking painkillers during pregnancy could affect the future fertility of the fetus, suggests research on human tissue and in mice.

Scientists at the University of Edinburgh and Copenhagen University Hospital in Denmark found human fetal testes and ovaries exposed to painkillers in a dish had reduced numbers of germ cells – which give rise to sperm and eggs. Researchers found these drugs also left chemical 'marks' on the DNA, which they suggest may also affect the fertility of future generations. The findings, published in the journal Environmental Health Perspectives, build on previous research in rats showing the use of painkillers during pregnancy may reduce the fertility of their offspring (BioNews 837).

'We would encourage women to think carefully before taking painkillers in pregnancy and to follow existing guidelines – taking the lowest possible dose for the shortest time possible,' said Dr Rod Mitchell at the University of Edinburgh who led the research.

Fetal ovaries in a dish exposed to paracetamol for one week had more than 40 percent fewer egg-producing germ cells. Researchers found the number of germ cells were almost halved after ibuprofen exposure. Females are born with a set number of eggs and a reduced number could lead to early menopause. 

Testicular tissue exposed to painkillers in vitro had around a quarter fewer sperm-producing germ cells. Researchers then used mice with human testicular tissue grafts – which mimic how testes develop in the womb. After one day with a human-equivalent dose of paracetamol, the number of germ cells had reduced by 17 percent. This dropped to almost a third fewer cells after one week.

Scientists also found that exposure to painkillers triggered mechanisms in the cells that make changes to the DNA's 'packaging' called epigenetic marks. These marks can be inherited, meaning the effects on fertility may be passed on to future generations.

Researchers found the effects of painkillers on germ cells were likely due to molecules called prostaglandins, which have key functions in the ovaries and testes.

'More research is needed into the long term effects of paracetamol and ibuprofen use in pregnancy on the fertility of the unborn child,' said Dr Patrick O'Brien, spokesperson for the UK's Royal College of Obstetricians and Gynaecologists. 'Women should not be alarmed by the results of this study. Paracetamol is widely accepted as a safe painkiller for pregnant women to take, and can be very beneficial when a pregnant woman is suffering with a migraine, for example.'

Researchers stress that advice for pregnant women remains unchanged. Current guidelines say that paracetamol should be used at the lowest possible dose for the shortest possible time. Ibuprofen should be avoided during pregnancy.