Taking painkillers during pregnancy could affect the fertility of unborn children in later life, and that infertility could be passed further down the family tree, according to new research by scientists at the University of Edinburgh in the UK.
Estimates suggest that one in three pregnant women take drugs such as paracetamol and ibuprofen, which could harm the fertility of both boys and girls.
The scientists exposed samples of human foetal testes and ovaries to paracetamol and ibuprofen for a week, and found that in ovaries exposed to paracetamol for a week, the number of egg-producing cells was reduced by 40 per cent.
In ovaries exposed to ibuprofen, the egg-producing cells were reduced by almost half.
This was significant, given that girls produce all their eggs in the womb, so being born with a reduced number could mean early onset of menopause, which in turn is associated with negative health outcomes such as osteoporosis.
The situation was not any better in boys, as testicular tissue exposed to paracetamol or ibuprofen had 25 per cent fewer sperm-producing cells.
The researchers also tested the effects of painkillers on mice with grafts of human foetal tissue, which mimic growth and function of testes in the womb.
After a day of treatment with a human-equivalent dose of paracetamol, the number of sperm-producing cells dropped by 17 per cent. After a week, there were almost one third fewer cells.
The painkillers’ effects on egg and sperm-producing cells are likely caused by their actions on molecules called prostaglandins, which have key functions in the ovaries and testes.
Researchers said that the findings add to growing evidence that medicines should be used with caution during pregnancy.
“We would encourage women to think carefully before taking painkillers in pregnancy and to follow existing guidelines,” said Dr Rod Mitchell, who led the research that was published in the journal Environmental Health Perspectives.
Women are usually advised to take the lowest possible dose of paracetamol for the shortest time possible, and to avoid ibuprofen during pregnancy. Aspirin is thought to be safe in low doses and some women are prescribed daily pills to reduce the risk of miscarriage.
Another study by researchers from the Hebrew University of Jerusalem showed a possible link between prolonged use of paracetamol (also called acetaminophen) during pregnancy and the risk of neurodevelopmental disorders in childhood.
An analysis of previous studies showed that prolonged exposure to paracetamol during pregnancy is associated with a 30 per cent increase in relative risk for attention deficit hyperactivity disorder (ADHD) and a 20 per cent increase in relative risk for autistic spectrum disorder (ASD).
The research data covered 132,738 mother and child pairs with a follow-up period of three to 11 years.
The researchers, however, said that the results should be interpreted with caution, noting that pain and fever during pregnancy can have a detrimental effect on the developing foetus and that paracetamol is still considered safe for use during pregnancy if taken for a short period.
Where symptoms persist, the woman should consult her physician for further treatment.
“The observed increase in risk was small and existing studies have significant limitations.
“While unnecessary use of any medication should be avoided in pregnancy, our findings should not alter current practice and women should not avoid use of short-term acetaminophen when clinically needed,” said Dr Ilan Matok, one of the researchers, in a study which appeared in the American Journal of Epidemiology.