How does closed system vitrification of human oocytes affect the clinical outcome? A prospective, observational, cohort, noninferiority trial in an oocyte donation program

Abstract

Objective: To evaluate whether is possible to vitrify oocytes in an aseptic (hermetically closed) fashion and maintain clinical results comparable with those of fresh oocytes.

Design: Prospective, observational, cohort, noninferiority trial.

Setting: Private in vitro fertilization center.

Patient(s): One hundred eighty-four recipients of donated vitrified oocytes.

Intervention(s): Closed system vitrification.

Main outcome measure(s): Pregnancy rate per cycle and clinical pregnancy rate per cycle.

Result(s): No statistically significant differences were observed between two groups regarding the pregnancy rate per cycle (63.1% vs. 60.9%) or the clinical pregnancy rate per cycle (55.4% vs. 58.7%). Biochemical pregnancy rate was statistically significantly higher in the fresh group (7.6% vs. 2.2%). The mean number of embryos transferred was similar (2.0 ± 0.0 vs. 1.97 ± 0.3). Concerning embryologic data, there were no statistically significant differences regarding the fertilization, cleavage, top quality day-3 embryo, or blastocyst rates, whereas the top quality blastocyst rate on day 5 was statistically significantly higher in the fresh oocyte group (31.7% vs. 26.1%).

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

Keywords: Aseptic technique; closed system vitrification; egg donor bank; oocyte donation; oocyte vitrification.