Is there a temporal trend in semen quality in Belgian candidate sperm donors and in sperm donors' fertility potential from 1995 onwards?

Background A recent meta-regression analysis reported a temporal trend in sperm count showing a significant decline in sperm count between 1973 and 2011. This decline is thought to affect fecundity. Moreover, semen quality is considered of key interest to public health given its association with all-cause male morbidity/mortality. The issue requires ongoing investigation due to geographical variation in semen quality and methodological errors in semen analysis. Objective To study whether there is a temporal trend in semen quality in Belgian candidate sperm donors and in sperm donors' fertility potential. Materials and Methods Retrospective analysis of samples provided by 439 candidate donors and pregnancy outcome in acceptors over a period of 23 years. RESULTS A total of 807 specimens from 439 candidate donors were examined from January 1995 to December 2017 (Table S1). Sub-analyses performed with regard to TSC from 2010 onwards (weighing) revealed a significant negative trend (R-2=-0.033; beta=-0.18; CI: -0.16 to 0.07; p < 0.05). We found a statistically significant association between year of donation and morphology (R-2= 0.036; beta= -0.19; CI: -0.26 to -0.08; p < 0.0001). The mean (+/- SD) clinical pregnancy rate per effective donor recruited (n = 104), defined as the number of women with a clinical pregnancy, per number of women who initiated treatment with a donor's spermatozoa, was 68.5 (+/- 24.9) %. This measure did not show a significant change in function of year of donation. Discussion Candidate sperm donors represent a select group of men; as such, these results are not to be interpreted as representative for the general population. Conclusion The study did not show a significant change in sperm concentration or fertility potential in sperm donors over a period of 23 years. However, a negative trend was found for TSC from 2010 onwards. Also, the results show a significant decrease in ideal morphology over time.