Studies have repeatedly linked maternal smoking during pregnancy with reduced sperm counts in male offspring. Now a research team at Lund University in Sweden has discovered that, independently of nicotine exposure from the mother, men whose fathers smoked at the time of pregnancy had half as many sperm as those with non-smoking fathers.
The study was conducted on 104 Swedish men aged between 17 and 20. Once the researchers had adjusted for the mother’s own exposure to nicotine, socioeconomic factors, and the sons’ own smoking, men with fathers who smoked had a 41 per cent lower sperm concentration and 51 per cent fewer sperm than men with non-smoking fathers. The research team at Lund University is the first to have reported this finding.
“I was very surprised that, regardless of the mother’s level of exposure to nicotine, the sperm count of the men whose fathers smoked was so much lower,” says Jonatan Axelsson, specialist physician in occupational and environmental medicine.
The biomarker cotinine is a metabolite from nicotine which can be measured in the blood. By measuring the level of cotinine, researchers can see whether the parents themselves smoke or whether they have been exposed to passive smoking. Many previous studies have shown that it is harmful to the fetus if the mother smokes but, in this study, the link between the father’s smoking habit and the son’s sperm count is even clearer.