Smoking during pregnancy may damage fertility of sons

"This is the first time we have been able to prove conclusively that male baby exposure to cigarette toxins in pregnancy and early life will damage later life fertility," said lead researcher Eileen McLaughlin, a professor at University of Newcastle in Australia.

For the study involving a mouse animal model, the researchers developed a machine that draws smoke into a nose piece.

They placed 27 female mice in the machine with their noses introduced into the nose piece. The amount of smoke inhaled represented the equivalent of a pack of 24 cigarettes a day in humans. Another 27 mice were exposed to normal air.

The 108 male mice offspring were examined regularly through to adulthood.

"Our results show that male pups of 'smoking' mothers have fewer sperm, which swim poorly, are abnormally shaped and fail to bind to eggs during in vitro fertilisation studies. Consequently, when these pups reach adulthood, they are sub fertile or infertile," McLaughlin added.

"We now know that exposure to cigarette toxins directly affects the stem cell population in the testes, causing a permanent reduction in the population of sperm produced," McLaughlin noted.

Although this is a study in mice, the findings are relevant to human health, the researchers pointed out.

The study appeared in the journal Human Reproduction.