Mothers who smoke early in pregnancy may sow the seeds of infertility in their unborn sons by arresting the development of sperm cells, research suggests.
Scientists found numbers of immature reproductive cells were much reduced in male embryos exposed to the effects of tobacco.
The findings echo those of previous research showing a similar effect on female embryos.
A team led by Professor Claus Andersen, from the University Hospital of Copenhagen, looked at 24 embryonic testes obtained from terminated pregnancies. They compared the number of germ cells – immature cells that become sperm in males and eggs in females – in the testes of embryos from smoking and non-smoking women.
Those from smokers contained less than half as many germ cells as those from non-smokers. The number of non-reproductive somatic cells was also reduced by more than a third in the testes of embryos from smoking mothers.
Previous research on the effect of smoking on female embryos found a similar pattern, said the researchers writing in the journal Human Reproduction.