研究開発・学会発表

【発表の概要】
Introduction:
The development of intracytoplasmic sperm injection (ICSI) created a new era in the field of assisted reproduction and revolutionized the assisted reproductive treatment (ART) protocols for couples with male factor infertility. In general, in the case of male subfertility, ICSI treatment results in higher fertilization rates per oocyte compared with conventional IVF treatment. Even the most severe cases of oligo-astheno-teratozoospermia (OAT) can now be successfully treated with ICSI. A dominant effect of a single suboptimal semen parameter on the fertilization results after IVF and ICSI was reported for sperm morphology and motility. However, only a few studies have mentioned semen quality (concentration and motility) in connection with the efficacy of ICSI performed with ejaculated spermatozoa. We determined whether the sperm concentration and motility in cases of oligozoospermia are associated with laboratory or clinical outcomes. The aim of this study was to explore the relationship between sperm quality and embryo development, pregnancy, and implantation rates as well as fetal loss in patients undergoing ICSI.
Materials and methods:
In this case study, we retrospectively analyzed data obtained from a total of 908 ICSI-ET cycles performed with fresh ejaculated spermatozoa. To exclude poor-responding patients, who would influence the results, couples in which the wife was older than 38 years were excluded. Then, the patients were divided into four treatment groups according to the results of an analysis of the husband’s semen: (A) mild oligozoospermia (10≤ Co. <20106/ml, n=283), (B) mild to severe oligozoospermia (5≤ Co. <10106/ml, n=192), (C) severe oligospermia (1≤ Co. <5106/ml, n=259), and (D) very severe oligozoospermia (0< Co. <1106/ml, n=174).
After 2-3 days of sexual abstinence, semen samples were produced by masturbation. All ejaculate-related ICSI procedures used fresh (not frozen) ejaculated spermatozoa. During oocyte retrieval, the patients were stimulated using standard GnRH agonist / FSH protocols. Fertilization was considered normal when two clearly distinct pronuclei (PN) containing nucleoli were present. The embryo cleavage of the 2PN oocytes was evaluated after a further 24 h of in-vitro culture (day 2). The embryos were scored according to the quality, number, and size of the blastomeres and the percentage of anucleate fragments. Cleavage-stage embryos were graded according to the criteria set out by Veeck. Clinical pregnancy was confirmed when the development of a gestational sac was observed by means of echographic screening at 7 days of pregnancy and the presence of a fetal heartbeat, and the implantation rate was determined by dividing the number of gestational sacs by the number of embryos transferred.
Results:
There were no significant differences in the background of the wife’s age, the evaluation of normal cleaved embryos (% of 2PN oocytes), and high quality embryos on day2 (% of cleaved embryos) after ICSI among the groups. However, the very severe oligozoospermia group (D) demonstrated a significantly lower percentage of 2PN oocytes compared with the other groups (73.6%, 78.4%, 71.4%, and 63.9%, Group A, B, and C vs. Group D, p<0.05). There was no significant difference in clinical pregnancy rates (38.2%, 38.0%, 36.7%, and 32.8%, respectively), implantation rates (24.5%, 21.4%, 21.9%, and 21.4%, respectively), or fetal loss (17.6%, 20.5%, 18.9%, and 19.3%, respectively).  Even when the treatment groups were selected based on sperm motility of < 40%, there were significant differences in zygote production (75.1%, 71.3%, 70.7%, and 63.8%, respectively, p<0.05) but not clinical pregnancy rates (36.6%, 31.5%, 37.5%, and 33.3%, respectively) among Group A, B, C, and D. In addition, no significant differences in zygote production or clinical pregnancy rates were detected between motility of < 40% and 40% in any group.
Conclusions:
Our data indicates the importance of selecting good quality sperm for oocyte injection especially in very severe oligozoospermia.