Although it is well known that mothers who smoke during pregnancy can have an adverse effect on their children's health, little is known about how paternal smoking in the time leading up to and during pregnancy can affect the health of offspring. (Shutterstock/File)
New European research has found that fathers who smoke before their children are conceived or born could be affecting the sperm quality of their future sons.
Carried out by researchers at Bispebjerg Frederiksberg Hospital in Denmark, the new study was a follow-up analysis of 778 young men all 19 years of age who had been born to mothers registered in the Danish National Birth Cohort between 1996 and 2002.
The researchers collected information on the parents' smoking status based on a maternal report made around gestational week 16.
The men's semen was assessed according to criteria set by the World Health Organization which includes sperm concentration, total sperm count, morphology (the size and shape of the sperm) and sperm motility (the ability of sperm to move).
The preliminary results showed that the sons of fathers who had smoked daily -- but whose mothers did not smoke -- had an 8 percent lower sperm concentration and 9 percent lower total sperm count than the sons of non-smoking fathers.
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Moreover, this association still held true even after other preconception and prenatal risk factors for adult semen quality such as parental age, alcohol and caffeine consumption or pre-pregnancy BMI (Body Mass Index) had been taken into account.
Although it is well known that mothers who smoke during pregnancy can have an adverse effect on their children's health, little is known about how paternal smoking in the time leading up to and during pregnancy can affect the health of offspring.
"There have been previous studies investigating the association of paternal smoking with semen quality but these were small studies without information on key confounders," said investigator Dr. Sandra Søgaard Tøttenborg. "Our larger study does support these previous findings that paternal smoking is associated with sperm concentrations in male offspring independently of maternal smoking."
However, Dr. Tøttenborg added that the effect would be even greater if the mother, and not the father, had smoked.
"Our results did show an association with paternal smoking,' said Dr. Tøttenborg, "but the effect of maternal smoking is much larger. If the mother but not the father smoked, the reduction was 26 percent for sperm concentration and 46 percent for sperm count. It's certainly worse for the boys if the mother smokes."
"Nevertheless, the circumstances in which the father smokes but the mother doesn't is much more prevalent, so this is still very relevant for public health. A decline in sperm count of 8 to 9 percent can seriously affect the fertility of men with already sub-optimal sperm quality."
The researchers say that paternal smoking may have this negative effect on sons' sperm quality due to smoking causing changes in the sperm genome, which may be then be transmitted to the cells of the children.
The results were presented on Tuesday by Dr. Tøttenborg at the 35th Annual Meeting of ESHRE (European Society of Human Reproduction and Embryology) in Vienna.