Sons are more likely to be born with undescended testicles - known as cryptorchidism - if their mother took painkillers during pregnancy, researchers found. The condition is a known risk factor for poor semen quality and testicular germ cell cancer in later life.
Lead author Henrik Leffers at Rigshospitalet in Copenhagen, Denmark, said the research 'suggests particular attention should be paid to the use of mild analgesics during pregnancy'.
Researchers analysed data from 2,297 women from Denmark and Finland on medication use during pregnancy. Baby boys were examined at birth for signs of cryptorchidism.
Women who used more than one analgesic simultaneously had a seven-fold increased risk of their sons having some form of the condition, compared with women who took nothing.
With multiple painkillers in the second trimester, this risk rose to 16-fold. Ibuprofen and aspirin individually quadrupled the risk of the condition, although no definitive link was found with paracetamol.
Dr Leffers said: 'We recommend that pregnant women seek advice from their physician before using mild analgesics.'