Abstract
BackgroundMaternal smoking during pregnancy has repeatedly been associated with decreased sperm counts in sons. Nevertheless, our team recently detected a lower total sperm count in the sons of smoking fathers as compared to sons of non-smoking fathers. Since paternal and maternal tobacco smoking often coincide, it is difficult to discriminate whether effects are mediated paternally or maternally when using questionnaire- or register-based studies. Therefore, getting an objective measure of the maternal nicotine exposure level during pregnancy might help disentangling the impact of paternally and maternally derived exposure.ObjectivesOur aim was to study how paternal smoking at the time of the pregnancy was associated with semen quality in the sons after adjusting for the maternal levels of nicotine exposure during pregnancy.MethodsWe recruited 104 men (17–20 years old) from the general Swedish population. The participants answered a questionnaire about paternal smoking. Associations between smoking and semen volume, total sperm count, sperm concentration, morphology and motility were adjusted for levels of the nicotine metabolite cotinine in stored maternal serum samples obtained from rubella screening between the 6th and 35th week of pregnancy. We additionally adjusted for the estimated socioeconomic status.ResultsAfter adjusting for the maternal cotinine, the men of smoking fathers had 41% lower sperm concentration and 51% lower total sperm count than the men of non-smoking fathers (p = 0.02 and 0.003, respectively). This was robust to the additional adjustment.ConclusionsOur results suggest a negative association between paternal smoking and sperm counts in the sons, independent of the level maternal nicotine exposure during the pregnancy.
Highlights
Maternal smoking during pregnancy has been associated with reduced sperm concentration in the sons in several studies [1,2,3,4,5,6], which is not the case for paternal smoking [2,3,4,5].in a study of young Swedish men, we detected that paternal smoking at the time of the pregnancy was negatively associated with both sperm concentration and the total sperm count [7]
Associations between smoking and semen volume, total sperm count, sperm concentration, morphology and motility were adjusted for levels of the nicotine metabolite cotinine in stored maternal serum samples obtained from rubella screening between the 6th and 35th week of pregnancy
After adjusting for the maternal cotinine, the men of smoking fathers had 41% lower sperm concentration and 51% lower total sperm count than the men of non-smoking fathers (p = 0.02 and 0.003, respectively)
Summary
In a study of young Swedish men, we detected that paternal smoking at the time of the pregnancy was negatively associated with both sperm concentration and the total sperm count [7]. We could neither exclude that the association between paternal smoking and lower sperm counts in the sons was rather due to a low socioeconomic status These two problems could be alleviated by adjusting for the actual level of maternal exposure to nicotine, measured in a biological matrix from the mother during a relevant period of time, as well as by trying to adjust for the socioeconomic position. Getting an objective measure of the maternal nicotine exposure level during pregnancy might help disentangling the impact of paternally and maternally derived exposure
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