Pregnant Smoking
Female environmental activists from the League of Independent Activists (IndyACT) wearing t-shirts depicting an infant, pretend to be pregnant as they stage a protest outside the parliament building in Beirut, March 16, 2011, where lawmakers are holding a session on the tobacco control law which is supposed to ban smoking in enclosed public spaces. Reuters/Cynthia Karam

An Australian study has revealed that women who smoke during pregnancy are at a risk of having boys with low sperm production in their adulthood.

In order to see how in later life men’s reproductive system is influenced by their early exposures in the womb, the researchers contacted men in their 20s whose mothers had participated in an infant and maternal health study during pregnancy two decades earlier.

They also carried out testicular ultrasounds on 404 men and collected sperm samples from 365 men. The study, published in The Journal of Clinical Endocrinology & Metabolism, looked at the median sperm production, which is the amount of sperm produced by at least half of the male participants in the study.

It was found that sperm production was around 19 percent lower among the men whose mothers had smoked during their pregnancy. Men born prematurely had lower testosterone in adulthood. The risk of premature birth goes up for women who smoke during pregnancy.

Lower testosterone levels may result in reduced sex drive, erectile dysfunction and low sperm count. The researchers also found that smoking may stunt growth in utero.

“It is harder for men with low sperm counts to conceive children, or it may take a longer time to make the partner pregnant ... If women want to have grandchildren, they shouldn't smoke,” researcher at the University of Copenhagen who wasn't involved in the study, Dr. Christine Wohlfahrt-Veje, told Reuters.

A healthy weight during childhood and adolescence may also help with reproductive health. They tend to have higher testosterone levels and larger testicular volume in adulthood. The only limitation of the study was that some of the men opted out of the testicular function test that may have biased the results.

However, lead study author, Dr. Roger Hart of the University of Western Australia, said that even then there is plenty of evidence to suggest women should refrain from smoking during pregnancy.

“It is a general healthy lifestyle message that women should not smoke in pregnancy, they should only start to try to conceive when they are in their optimal health, and when any co-existing medical conditions have been optimized, as this is associated with good foetal growth through pregnancy and a reduced risk of premature delivery,” Hart said.

He said that among other things, smoking during pregnancy may impair brain development in utero, increase complications during pregnancy, lead to premature birth and also increase the odds of breathing problems and other childhood health problems such as hyperactivity.