Choice of underwear and male fecundity in a preconception cohort of couples.

Our objective was to investigate the relationship between male underwear-type worn during daytime/bedtime and male fecundity as measured by semen quality and time-to-pregnancy. We used data from a prospective preconception cohort conducted in 16 counties in Michigan and Texas, USA. 501 couples were enrolled and followed for 12 months of trying, which facilitated capture of time-to-pregnancy (in cycles), 6-cycle conception delay, and 12-month infertility. Male partners provided semen samples via in-home collection for next-day semen analysis comprised of 35 semen quality endpoints. At enrollment, men provided information on type of underwear worn during daytime and bedtime and were classified into 6 categories by underwear choice (n = 491): (i) briefs day/night, (ii) boxer-briefs day/night, (iii) boxers day/night, (iv) briefs day and boxers/none at night, (v) boxer-briefs day and boxers/none at night, (vi) boxers day and none at night. 473 (96%) men had semen analysis performed. Men switching from their usual daytime underwear to boxers/none for bed (groups 4, 5, 6) had the most evidence of change in semen quality endpoints (10 of 11 differences) relative to men wearing briefs day/night (group 1). Group 4 men had lower percent of sperm with coiled tail (β = -0.18, 95% CI: -0.35, -0.01), higher percent round (β = 0.22, 95% CI: 0.01, 0.42), number of immature sperm (β = 0.44, 95% CI: 0.11, 0.77), and amplitude head displacement (β = 0.57, 95% CI: 0.10, 1.03). Group 5 men had higher sperm head perimeter (β=0.17, 95% CI: 0.002, 0.34), amplitude head displacement (β = 0.47, 95% CI: 0.03, 0.91), percent cytoplasmic droplet (β = 0.44, 95% CI: 0.11, 0.77) and high DNA stainability (β=0.39, 95% CI: 0.01, 0.78). After false discovery rate control, no differences remained significant. No significant differences in time-to-pregnancy, conception delay, or infertility were observed. In summary, male underwear choice is associated with few differences in semen parameters; no association with time-to-pregnancy is observed providing reassurance to couples attempting pregnancy. Published 2016. This article has been contributed to by US Government employees and their work is in the public domain in the USA.