Parental Educational Attainment at Birth and Biomarkers of Male Fecundity: A Study From the Danish National Birth Cohort

Background: Low parental education is associated with poorer offspring health, but its influence on male fecundity remains unclear. Objective: To study the association between parental educational attainment at birth and biomarkers of male fecundity in young men and to explore whether this association is mediated by maternal smoking in pregnancy and overweight/obesity at 19 years of age. Materials and Methods: A cohort study with 1058 sons born 1997–1999 from the Fetal Programming of Semen Quality (FEPOS). The exposure was the highest educational attainment among parents at their child's birth, obtained from administrative registers. Outcomes were measured at a clinical examination and included semen characteristics (semen volume, semen concentration, total sperm count, motility, morphology, DNA fragmentation index, and high DNA stainability), testicular volume, and reproductive hormone levels (estradiol, testosterone, Sex Hormone-Binding Globulin, luteinizing hormone, and follicle-stimulating hormone). Outcomes were analyzed using a multivariable negative binomial regression model adjusted for potential confounding factors and precision variables. Potential mediation by maternal smoking in pregnancy, as well as overweight or obesity at 19 years of age, was investigated in separate mediation analyses. Results: Sons of parents with low educational attainment at birth had a tendency to have lower semen volume (relative percentage difference: −8% (95% confidence interval [CI]: −17%; 2%), lower semen concentration (−8% [95% CI: −20%; 6%]) and lower total sperm count (−12% [95% CI: −25%; 3%]) compared to sons of parents with high educational attainment. No major difference was observed for other biomarkers of male fecundity. Maternal smoking in pregnancy, but not overweight/obesity at 19 years of age, partly mediated the association. Conclusion: Our findings suggest some association between parental educational attainment and biomarkers of male fecundity in young men. These findings were partly mediated by maternal smoking in pregnancy, but not by overweight or obesity in young adult sons.