Mothers who smoke while pregnant may put their sons at risk of infertility later in life, an increasing body of research suggests.
The newest study findings reveal that the more cigarettes mothers smoke during pregnancy, particularly their last month, the lower their sons' total sperm count in adulthood will be
"An increasing number of couples seek infertility treatment, which makes poor semen quality and infertility a major public health problem," study co-author Cecilia Høst Ramlau-Hansen, a doctoral student at Aarhus University Hospital in Denmark, told Reuters Health.
"If maternal smoking during pregnancy in fact is a cause of poor semen quality in the sons, this is a factor that can be prevented," she added.
Semen quality decreasing
Previous researchers have also reported an association between prenatal tobacco smoke exposure and semen quality but the results were not consistent. Also, many studies relied on the study participants' recall of their smoking history while pregnant.
The quality of men's semen has reportedly decreased over the past 60 to 70 years, with as many as one in four Danish men, among others, experiencing fertility problems as a result of their low sperm concentration, according to Ramlau-Hansen.
For the current study, Ramlau-Hansen and her colleagues investigated semen quality in 347 men, ages 18 to 21 years, born to women in the "Healthy Habits for Two" study. In this study, conducted in the mid-1980s, pregnant women were asked about their smoking habits and other lifestyle information.
Lower sperm count
The men were ranked according to the extent of their exposure to tobacco smoke in utero. Ninety-nine were born to non-smokers. The 248 men who were exposed to tobacco smoke in utero had a lower total sperm count than did their nonexposed peers, study findings indicate.
Those exposed to the highest amounts of tobacco smoke - more than 19 cigarettes a day - had a 19-percent lower semen volume, a 38-percent lower total sperm count and a 17-percent lower sperm concentration, than did unexposed men, Ramlau-Hansen and her team report in the American Journal of Epidemiology.
The findings may be "spurious or due to chance" the researchers acknowledge, but "it is not unexpected that exposures during the time period of testes development may impair spermatozoa production 20 years later in life," they write.
The major metabolite of nicotine, cotinine, is known to cross the placenta and it may also be able to cross the barrier between the blood and the testes, research suggests. Other components of tobacco smoke may also have a direct toxic effect on the foetal testes.
"If smoking during pregnancy increases the risk of poor semen quality in the sons, the risk of infertility for the sons also increases," Ramlau-Hansen said. "For some of the...mothers it will probably mean that their chances of becoming a grandmother one day decreases," she added. – (ReutersHealth)
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