Comparison between semen parameters in specimens collected early in the morning and in the evening

The majority of facilities in Japan that offer artificial insemination as part of assisted reproduction programs currently perform semen collection in the early morning. The total motile sperm count of the semen used in intrauterine insemination is an important factor in achieving successful fertilization and subsequent childbirth. The present study was initiated to determine whether semen parameters varied with the time of day at which the semen sample was collected. The study subjects were 20 fertile males and 20 infertile males with abnormal seminograms who attended our Reproduction Center. Semen was collected early in the morning (morning collection group) and in the evening (evening collection group) from the same subjects, and total motile sperm count was assessed as the primary outcome measure. As secondary outcome measures, semen volume, sperm concentration, sperm motility and total sperm count were assessed. A sexual abstinence period of 3 days was set for all participants. The semen samples were analyzed using CASA CEROS, a sperm motility analysis system, and the data from the morning and evening collection groups were compared using a Wilcoxon signed rank test. We found that the fertile males had a significantly higher total motile sperm count and total sperm count in the evening collection group than in the morning collection group. In contrast, the male infertility patients showed no significant difference in total sperm count between the two collection times; however, the total motile sperm count was significantly higher in the evening collection group than the morning collection group. Our analyses indicate that total motile sperm count in ejaculated semen is significantly higher after evening collection than after morning collection. From a male side perspective, we suggest that successful intrauterine insemination might be easier to achieve using semen collected in the evening than in the early morning.Abbreviations: IUI: intrauterine insemination; OAT: oligoasthenoteratozoospermia; TSC: total sperm count; TMSC: total motile sperm count.