Effect of cryopreservation on quality and fertilization capacity of human sperm N. Marcus-Braun * , G. Braun, G. Potashnik, I. Har-vardi IVF Unit, Department of Obstetric and Gynecology, Faculty of Health Sciences, Soroka University Medical Center, Ben-Gurion University of the Negev, P.O. Box 151, Beer-Sheva 84101, Israel Received 10 January 2003; received in revised form 27 October 2003; accepted 14 January 2004 Abstract Objective: To analyze retrospectively the effect of cryopreservation on donor’s sperm. Study design: Data were collected on 178 cryopreserved-thawed sperm specimens from 44 donors and 624 oocytes from 62 women, which underwent in vitro fertilization-embryo transfer (IVF-ET) treatments with donor’s sperm. Data on fresh sperm, 175 sperm specimens from 76 couples which underwent IVF-ET treatments, were used as a control group. Semen analysis was done by cell concentration, percent of motility, and quality of motility according to the World Health Organization (WHO) recommendation. Sperm quality parameters which had the strongest impact on fertilization capacity were determined using the statistical response surface model and conjoint analysis. Results: Passing sperm through Percoll column decreased sperm concentration, with no improvement in sperm motility but with a slight increase in quality of motility. Quality of motility of donor’s sperm had the strongest impact on fertilization capacity. Conclusion: Current freezing–thawing protocols of sperm cause a decrease in sperm parameters without affecting fertilization capacity. Furthermore, quality of motility of frozen–thawed sperm seems to be a significant measure of sperm fertilization capacity. # 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Sperm; Donor; Fertility rate; Cryopreservation; Quality; Conjoint analysis 1. Introduction The use of donor sperm is an integral part of in vitro fertilization-embryo transfer (IVF-ET) in couples with male infertility and in single women. Freezing donor’s sperm, in order to prevent sexually transmitted diseases, enhances the importance of defining the quality and the fertilization capacity of sperm, following processes of freezing and thawing (1). The fertilization potential of cryopreserved- thawed sperm has been studied for more than 50 years [2–5]. Until recently there has been no sufficient information available in the literature and no conclusive evidence regard- ing sperm fertilization capacity following freezing and thawing as compared with fresh sperm. In some clinical studies, frozen–thawed sperm had a lower fertilization capacity when compared with fresh sperm [6,7]. However, in other studies no significant difference between frozen– thawed and fresh sperm was observed [8,9]. Sperm mor- phology was analyzed in a few studies. In most of the cases, sperm morphology was found to be unaffected by the freezing–thawing processes [10–12]. It is known that pas- sage of sperm cell through Percoll column in preparation for IVF-ET improves sperm motility and fertilization capacity of the sperm [13]. However, the linkage between sperm quality following freezing–thawing procedures and its fer- tilization capacity has not yet been well established [1,14]. The present study was designed to investigate the effect of the freezing–thawing process on sperm quality parameters. An attempt was also made to identify the most sensitive parameter which can predict sperm fertilization capacity. 2. Materials and methods This study was performed at the IVF unit of the Soroka Medical Center, Beer-Sheva, Israel. The study was retro- spective by nature, based on data which was collected between the years 1990 and 1998. 2.1. Study population Sperm quality parameters and sperm data were collected from 178 sperm specimens obtained from 44 donors. All European Journal of Obstetrics & Gynecology and Reproductive Biology 116 (2004) 63–66 * Corresponding author. Tel.: þ972-8-6518954; fax: þ972-8-6519492. E-mail address: braung@012.net.il (N. Marcus-Braun). 0301-2115/$ – see front matter # 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejogrb.2004.01.036