Prolonged paracetamol use by pregnant women may reduce testosterone production in unborn baby boys, according to UK researchers.
They believe their findings – based on research in mice – could help to explain reported links between paracetamol use in pregnancy and reproductive health problems in young boys.
The authors recommend that expectant mothers should follow existing guidelines that the painkiller – the primary medicine used for managing pain and fever during pregnancy – be taken at the lowest effective dose for the shortest possible time.
“Ideally, women should avoid taking medicines when they are pregnant”
The Edinburgh University study tested the effect of paracetamol on testosterone production in mice carrying grafts of human testicular tissue to mimic how the developing testes grow and function during pregnancy.
Scientists gave the mice a typical daily dose of paracetamol – over a period of either 24 hours or seven days. They measured the amount of testosterone produced by the human tissue an hour after the final dose of paracetamol.
They found there was no effect on testosterone production following 24 hours of paracetamol treatment. After seven days of exposure, however, the amount of testosterone was reduced by 45%.
The research is published in the journal Science Translational Medicine.
Study author Dr Rod Mitchell said: “This adds to existing evidence that prolonged use of paracetamol in pregnancy may increase the risk of reproductive disorders in male babies.
“We would advise that pregnant women should follow current guidance that the painkiller be taken at the lowest effective dose for the shortest possible time.”
Carmel Lloyd, head of education at the Royal College of Midwives, said: “If women do take medicines such as paracetamol when they are pregnant, they should use the lowest effective dose for the shortest possible time.
But she added: “Ideally, women should avoid taking medicines when they are pregnant, particularly during the first three months. Minor conditions such as colds or minor aches and pains often do not need treating with medicines.”
Professor Maureen Baker, chair of the Royal College of GPs, said: “Existing evidence shows that, in the main, paracetamol is a safe drug for the majority of patients.
“But this study – and other recent studies – call this into question and it is important that we take new research into account and shape updated guidelines for healthcare professionals in the best interests of all patients,” she said.