Pregnant women using paracetamol for prolonged periods may reduce the fertility of their unborn sons, research has found.
Scientists at the University of Edinburgh said their study suggests too much paracetamol in pregnancy may reduce testosterone production in male babies.
They said expectant mothers should follow existing NHS guidelines that the painkiller be taken at the lowest effective dose for the shortest possible time.
Research carried out on mice found rodents given three doses of paracetamol a day for a week had a 45% reduction in testosterone compared to a placebo.
The hormone, which is produced in the testicles, is crucial for life-long male health. Reduced exposure to testosterone in the womb has been linked to an increased risk of infertility, testicular cancer and undescended testicles.
The study saw scientists test the effect of paracetamol on mice carrying grafts of human testicular tissue, which have been shown to mimic how the developing testes grow and function during pregnancy.
The research is published in the journal Science Translational Medicine.