Closed vs. Open Oocyte Vitrification Methods Are Equally Effective for Blastocyst Embryo Transfers: Prospective Study from a Sibling Oocyte Donation Program

Abstract

Purpose: To assess whether open and closed vitrification protocols are equally effective for sibling-oocyte cycles when performing blastocyst embryo transfers.

Materials and methods: A prospective study was set up comparing the open and the closed vitrification techniques in oocyte recipients sharing sibling oocytes between 2014 and 2016. Sibling oocytes were randomly and equally assigned into the closed group (oocytes vitrified in a closed system) or the open group (oocytes vitrified in an open system). Intracytoplasmic sperm injection was performed on all cases. Embryo transfers were performed on day 5. Power analysis calculation showed that 94 cycles would be needed for each group in the study in order to achieve statistical significance at a 5% level with power 80%.

Results: The final number of donors included was 95. A total of 190 recipients matched with their donors were included in the study. There was no difference in the mean number of oocytes vitrified with the closed or the open system (8.26 ± 2.54 vs. 8.31 ± 2.57). No significant difference was observed between the 2 groups regarding survival rate, fertilization rate, cleavage rate, top-quality embryos on day 3, blastocyst rate, and top-quality blastocyst rate. Moreover, no statistically significant difference in the b-human chorionic gonadotropin-positive rate, clinical pregnancy rate per cycle, implantation rate, ongoing pregnancy rate, and live birth rate between closed and open groups.

Conclusion: Οpen and closed vitrification protocols are equally effective for sibling-oocyte cycles.

Keywords: Infertility; Oocyte donation; Vitrification.