Painkillers could harm future fertility of subsequent offspringCredit:Dominic Lipinski/PA Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. After just one day of treatment with a human-equivalent dose of paracetamol, the number of sperm-producing cells in the graft tissue had dropped by 17 per cent. After a week of drug treatment, there were almost one third fewer cells.Previous studies with rats have shown that painkillers administered in pregnancy led to a reduction in germ cells in female offspring. This affected their fertility and the fertility of females in subsequent generations.The scientists found that exposure to paracetamol or ibuprofen triggers mechanisms in the cell that make changes in the structure of DNA, called epigenetic marks.These marks can be inherited, helping to explain how the effects of painkillers on fertility may be passed on to future generations.The effects were likely to be caused by the impact on molecules called prostaglandins, which have key functions in the ovaries and testes, researchers said.The study, published in Environmental Health Perspectives, was funded by the Medical Research Council, Wellcome and the British Society of Paediatric Endocrinology and Diabetes.Dr Rod Mitchell, who led the research at the University of Edinburgh’s MRC Centre for Reproductive Health, said: “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.”Recent French research found that taking ibuprofen for just two days during pregenancy was enough to result in fertility problems in subsequent female children born. Even if women stop taking the painkiller, the damage is irreversible, scientists warned.The NHS advises pregnant women to avoid ibuprofen during the first six months, because it has been linked to an increased risk of miscarriage. If pain relief is required, paracetamol is advised, with the “lowest effective dose for the shortest time possible” recommended. Pregnant women are categorically told not to take ibuprofen in late pregnancy, because of an increased risk of complications.Dr Channa Jayasena, senior clinical jecturer in reproductive endocrinology at Imperial College London, said: “Paracetamol and ibuprofen are commonly used during pregnancy. However, over the last year, a growing number of reports have suggested that we might need to take a closer look at their safety in unborn babies. This latest study raises the possibility that paracetamol and ibuprofen may reduce the growth of the ‘germ cells’ which later become eggs or sperm in unborn babies.”She said that the study only looked at tissue in the lab, but should be considered along side other similar research.“While it is still premature to stop taking these important drugs, there is a growing case to investigate their safety for pregnant women,” she said.Dr Sarah Branch, deputy director of the MHRA’s vigilance and risk management of medicines division, said: “Women should avoid taking medicines during pregnancy unless absolutely necessary and should speak to their doctor, midwife or pharmacist before doing so.”John Smith, chief executive of the Proprietary Association of Great Britain said: “The official NHS advice on paracetamol is that it can be used through all stages of pregnancy to reduce a high temperature (fever) and relieve pain. This is supported by a large body of evidence from over 50 years of paracetamol use in humans.“This study also looked at the use of ibuprofen in pregnancy, however pregnant women are advised to avoid taking ibuprofen during pregnancy, unless it is on the advice of a doctor.” We would encourage women to think carefully before taking painkillers in pregnancyDr Rod Mitchell, University of Edinburgh Taking common painkillers including paracetamol during pregnancy could make their grandchildren infertile, research suggests.Previous studies have found that the drug ibuprofen could harm the fertility of girls.Women are advised to avoid the medication during pregnancy, and told that if pain relief is needed, they should take paracetamol for as little time as possible.But the new study found that both drugs could harm future fertility of subsequent offspring – with an impact on boys as well as girls.Estimates suggest around one in three will take such drugs during pregnancy.The study found that the medication made marks on the DNA, with permanent consequences. Ovaries exposed to paracetamol for one week had more than 40 per cent fewer egg-producing cells. After ibuprofen exposure, the number of cells was almost halved.And testicular tissue exposed to painkillers in a culture dish had around a quarter fewer sperm-producing cells after exposure to paracetamol or ibuprofen.Scientists at the University of Edinburgh looked at the effects of paracetamol and ibuprofen on samples of human fetal testes and ovaries. They found similar effects using several different experimental approaches, including lab tests on human tissue samples and animal studies.Human tissues exposed to either drug for one week in a dish had reduced numbers of cells that give rise to sperm and eggs, called germ cells, the study found.Girls produce all of their eggs in the womb, so if they are born with a reduced number it could lead to an early menopause.The team also tested the effects of painkiller treatment on mice that carried grafts of human fetal testicular tissue. These grafts have been shown to mimic how the testes grow and function during development in the womb.