No abstract

The use of open carriers for embryo vitrification has raised safety concerns and therefore vitrification in closed systems has been proposed. However, the drop in the cooling rate emerges as a major drawback. The objective of the present study was to compare the efficiency of vitrification in open versus closed conditions. Blastocysts were randomly allocated either to open ultra-rapid vitrification (group I) or closed aseptic vitrification (group II). In group I, blastocysts were exposed to two solutions of ethylene glycol/dimethylsulphoxide (10%/10% and 20%/20%), while in group II, blastocysts were pretreated with a solution of lower concentration (5%/5%). A total of 208 and 224 vitrification-warming cycles were performed for groups I and II, respectively. Both groups were equal in terms of maternal age, sperm parameters and number and quality of blastocysts vitrified, warmed and transferred per cycle. Importantly, there was no significant difference between the groups in the analysed outcomes; embryo survival rate (84.1% versus 82.1%), clinical pregnancy rate (45.9% versus 42.4%), implantation rate (25.6% versus 24.5%), cycle cancellation rate (6.7% versus 8.5%) and live birth rate (41.2% versus 41.0%). These data suggest that ultra-rapid vitrification may be replaced by aseptic vitrification without affecting clinical efficiency.

In conventional IVF cycles with total fertilization failure, rescue intracytoplasmic sperm injection (ICSI) performed 24h after insemination has yielded poor results. However, when ICSI is used, total fertilization failure is a rare event. The aim of the present study is to investigate the degree of sperm contribution to fertilization failures using the egg-sharing model in oocyte donor cycles. The study included only the oocyte donor cycles of sibling oocytes with total fertilization failure in at least one of the matched recipients. Oocytes from 49 oocyte donor cycles were equally shared among 98 recipients undergoing conventional IVF. Due to total fertilization failure in half of the recipients, rescue ICSI was carried out. Compared with the conventional IVF only group, the rescue ICSI group had a lower pregnancy rate (30.61% versus 71.43%), clinical pregnancy rate (28.57% versus 67.35%) and ongoing pregnancy rate (28.57% versus 63.27%) (all P<0.01). Cryptic sperm defects in apparently normal spermatozoa may be the cause of total fertilization failure, indicating the need for simple routine tests to detect them.

The effect that gonadotrophin-releasing hormone (GnRH) antagonists exert on endometrial receptivity has not yet been elucidated. GnRH antagonists might directly affect oocytes, the embryo and/or the endometrium. The aim of this study was to investigate the direct effect of GnRH antagonists on the endometrium in oocyte donation cycles. In an oocyte donation programme, oocytes from each donor (n = 49), stimulated with gonadotrophins and a GnRH antagonist, were equally shared between two different matched recipients. Recipients were randomly allocated to either receive a GnRH antagonist concomitant to donor during their endometrial priming with oestradiol (group I, n = 49) or to solely continue with their endometrial preparation (group II, n = 49). Pregnancy rate was 55.1% in group I and 59.1% in group II. Implantation rate was 26.1% in group I and 24.4% in group II. Endometrial thickness was also similar between the two groups on the day of human chorionic gonadotrophin injection to the donor. In conclusion, GnRH antagonist administration during the proliferative phase at a dose of 0.25 mg per day does not appear to adversely affect endometrial receptivity in oocyte recipients.

Aseptically (in a closed system) vitrified oocytes show similar clinical efficiency compared with their sibling fresh oocytes.