Maternal coffee consumption and biomarkers of reproductive health in young, adult sons: a cohort study

It has been proposed that poor semen quality may have its origins from fetal programming due to environmental factors. We investigated whether maternal coffee consumption during early pregnancy was associated with biomarkers of reproductive health in adult sons in the Fetal Programming of Semen Quality (FEPOS) cohort. In 2017-2019, 1,058 young men provided a semen and blood sample and self-measured their testis volume. Daily maternal coffee consumption was reported by the mothers around gestational week 17. We estimated relative percentage differences with 95% confidence intervals (CI) for semen quality measures, testis volume, and reproductive hormone levels according to maternal coffee consumption during pregnancy. Maternal coffee consumption (yes/no (reference)) was associated with lower semen volume (-7.0% (95% CI:-12.9;-0.7)), lower proportion of morphologically normal spermatozoa (-8.3% (95% CI:-16.5;0.8)), higher proportion of non-progressive and immotile spermatozoa (4.3% (95% CI:-1.5;10.3)), and lower testis volume (-4.8% (95% CI:-9.0;-0.4)). No indication of a dose-response association or threshold effects was observed in the categorized and continuous analyses. No associations with reproductive hormone levels were observed in any of the analyses. Overall, the study does not provide obvious indications that maternal coffee consumption in early pregnancy deteriorates male offspring fecundity. While some minor changes were observed, most estimates were small with confidence intervals overlapping the null. Future studies, preferably with greater exposure contrast, are warranted before a conclusion can be drawn as to whether maternal coffee consumption during pregnancy constitutes a risk for reproductive health in adult sons.