The use of marijuana has been increasing among U.S. men of reproductive age and its recreational consumption was legalized in Washington State (WS) on November 12th, 2012. Marijuana and its active metabolite tetrahydrocannabiol (THC) can alter the signaling system within spermatozoa which may result in negative effects on spermatogenesis and male fertility. We aimed to characterized differences in semen quality among men with variable consumption of marijuana. Prospective cohort study. We prospectively evaluated semen analyses (SA) from men who presented for infertility evaluation at a single male fertility laboratory. Semen analyses were performed from July 2017 to April 2018. All participants completed a reproductive health questionnaire which included specific queries on past and present marijuana consumption. Questionnaire data included age, ethnicity, marijuana use (≤1 or >1 time per week), duration (months), and tobacco smoking. SA was performed in accordance with World Health Organization (WHO) 2010 criteria. SA parameters included volume (mL), concentration (million/mL), motility (%), progressive motility (%), rapid and linear motility (%) and strict normal morphology (%). A total of 409 patients underwent SA and completed the questionnaire of which 174 (43%) men reported marijuana use (ever users.) Among the ever users, current and past users compromised 71 (18%) and 103 (25%) respectively. Compared to non-user, semen quality was significantly decreased in volume, concentration, morphology, total motile count (TMC) and total progressive motile count (TPMC) compared to never users (Table 1). In multivariate logistic regression analyses, controlling for age, marijuana use was associated with increased odds of abnormal morphology (OR 2.28 (95% confidence interval (CI): 1.52-3.43)), volume (OR 2.02 (1.04-3.94)), and TPMC (OR 1.8 (1.05-3.06)). There was no significant association between marijuana use and sperm concentration, motility or progressive motility as solitary parameters. Marijuana use is common among men presenting for fertility evaluation in our cohort and may have a detrimental effect on semen quality, particularly morphology, volume, and TPMC. Given these findings, large, prospective studies of both semen quality and fertility in this growing, at-risk population are warranted.Table 1Percentages of normal and abnormal semen analysis [WHO 2010] among three groupsParametersGroupNormal Semen Analysis N (%)Abnormal Semen Analysis N (%)P valueVolumeNever216 (92%)19 (8%)0.044Past93 (90%)10 (10%)Current58 (82%)13 (18%)ConcentrationNever209 (89%)26 (11%)0.086Past87 (85%)16 (15%)Current56 (79%)15 (21%)% MotilityNever145 (62%)90 (38%)0.011Past75 (73%)28 (27%)Current56 (79%)15 (21%)% Progressive motilityNever162 (69%)73 (31%)0.513Past73 (71%)30 (29%)Current54 (77%)17 (23%)% Strict morphologyNever156 (67%)79 (33%)0.000Past48 (47%)55 (53%)Current35 (49%)36 (51%)Total motile countNever199 (85%)36 (15%)0.608Past84 (82%)19 (18%)Current57 (80%)14 (20%)Total progressive motile countNever204 (87%)31 (13%)0.111Past83 (81%)20 (19%)Current55 (76%)16 (23%) Open table in a new tab