Improved sperm kinematics in semen samples collected after 2 h versus 4-7 days of ejaculation abstinence.

<bold>Study Question: </bold>Does a short abstinence period of only 2 h yield spermatozoa with better motility characteristics than samples collected after 4-7 days?<bold>Summary Answer: </bold>Despite lower semen volume, sperm concentration, total sperm counts and total motile counts, higher percentages of motile spermatozoa with higher velocity and progressiveness were detected in samples obtained after 2 h.<bold>What Is Known Already: </bold>Most studies that have assessed the effect of abstinence periods on sperm motility parameters in men with a sperm concentration below 15 million/ml have detected a higher percentage of motile spermatozoa in samples obtained after short abstinence periods. Studies of men with sperm concentrations above 15 million/ml have reported significantly decreased motile sperm counts after 24 h of abstinence compared with longer abstinence periods.<bold>Study Design, Size, Duration: </bold>This study had a controlled repeated-measures design based on semen samples from 43 male partners, in couples attending for IVF treatment, who had a sperm concentration above 15 million/ml. Data were collected between June 2014 and December 2015 in the Fertility Unit of Aalborg University Hospital (Aalborg, Denmark).<bold>Participants/materials, Setting, Methods: </bold>Participants provided a semen sample after 4-7 days of abstinence followed by another sample after only 2 h. For both ejaculates, sperm concentration, total sperm counts, motility groups and detailed kinematic parameters were assessed and compared by using the Sperm Class Analyzer (SCA) computer-aided sperm analysis system before and after density gradient selection. The laboratory's local manual method (Makler chamber) was used for comparison.<bold>Main Results and the Role Of Chance: </bold>The second raw ejaculate demonstrated lower semen volume (P < 0.0001), sperm concentration (P = 0.003) and sperm counts in all motility sub-groups (P < 0.001) but higher percentages of spermatozoa with higher velocity (P < 0.01), progressiveness (P < 0.001) and hyperactivation (P < 0.001), compared with the first raw ejaculate.<bold>Limitations, Reasons For Caution: </bold>The first ejaculate in this study was also used for the IVF/ICSI treatments and therefore only patients with a semen volume ≥2 ml and concentration ≥15 million/ml were included. Further validation in large prospective randomized controlled trials, more purposely directed at normozoospermic males with partners having problems conceiving when there appears to be no female factor, is needed to confirm the potential advantage of using a second semen sample in improving fertilization and pregnancy rates in assisted reproduction.<bold>Wider Implications Of the Findings: </bold>Despite the significantly lower semen volume, sperm concentration and total sperm counts in all motility sub-groups, the significantly higher percentage of spermatozoa with better motility characteristics (velocity, progressiveness and hyperactivation) in the second ejaculate, may provide and allow for a simpler and more effective selection of higher quality spermatozoa. This could prove to be an advantage for ART procedures such as intracytoplasmic sperm injection where a large number of spermatozoa is not needed. It can also be speculated that pooling two consecutive ejaculates obtained after 4-7 days and after 2 h, could be an advantage for intrauterine insemination where a large number of motile spermatozoa are needed.<bold>Study Funding/competing Interest(s): </bold>This study was supported by internal grants from the Department of Health Science and Technology, Faculty of Medicine, Aalborg University (Aalborg, Denmark). The SCA® was provided by a grant from 'Ferring Pharmaceuticals' to Aalborg University Hospital (H.I.N). G.V.D.H. is an external senior scientific consultant to Microptic S/L (Barcelona, Spain). H.A. has provided scientific input and presentations for Microptic S/L (Barcelona, Spain) on several occasions. All other authors declare no conflict of interest.<bold>Trial Registration Number: </bold>N/A. [ABSTRACT FROM AUTHOR]