Studies have repeatedly linked maternal smoking during pregnancy with the reduction of sperm count in male offspring. Now, a research team at Lund University in Sweden found that, regardless of the mother's nicotine exposure, men whose parents smoked at the time of pregnancy had half as much sperm as non-smoking parents.
The study was conducted on 104 Swedish men between 17 and 20 years old. Once the researchers adjusted the mother's exposure to nicotine, socioeconomic factors, and smoking habits of the children, men with parents who smoked had a 41% lower sperm concentration and 51% less Sperm than men with non-smoking parents. The research team at the University of Lund is the first to report this finding.
"I was very surprised that, regardless of the level of exposure of the mother to nicotine, the sperm count of men whose parents smoked was much lower," says Jonatan Axelsson, a medical specialist in occupational and environmental medicine.
The cotinine biomarker is a metabolite of nicotine that can be measured in the blood. By measuring the level of cotinine, researchers can see if the parents smoke or if 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 smoking habit of the father and the sperm count of the child is even clearer.
Jonatan Axelsson can not explain why this is the case and thinks that more research is needed to understand the underlying mechanisms. On the other hand, he explains, similar studies have also shown links between smoking parents and various health outcomes in children, such as malformations.
"Unlike the maternal ovum, the father's gametes are continually divided throughout life and mutations often occur at the precise moment of cell division.We know that tobacco smoke contains many substances that cause mutations, so that one can imagine that, at the moment of conception, gametes have undergone mutations and, therefore, transmit genes that reduce the quality of sperm in male offspring. "
Most new mutations (known as de novo mutations) occur through the father and there are also links between the father's age and several complex diseases. In addition, researchers have observed that smoking is related to DNA damage in sperm and that smokers have more breaks in the DNA chain. It has been reported that the children of parents who smoke have up to four times more mutations in a certain repetitive part of the DNA than the children of parents who do not smoke.
"We know that there is a link between the sperm count and the chances of pregnancy, so it could affect the possibility that these men have children in the future." The father's smoking is also linked to a shorter reproductive life in the daughters, so the notion that everything depends on whether the mother smokes or not does not seem convincing, future research could perhaps bring us closer to a causal link, "concludes Jonatan Axelsson.
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