Does duration of cryostorage affect survival rate, pregnancy, and neonatal outcomes? Large‐scale single‐center study of slush nitrogen (SN<sub>2</sub>) vitrified‐warmed blastocysts
Hye Nam Lee, Jae Kyun Park, Soo Kyung Paek, Ji Hyun Byun, Haengseok Song, Hee Jun Lee, Eun Mi Chang, Ji Won Kim, Woo Sik Lee, Sang Woo Lyu
Abstract
Abstract Objective To evaluate the effects of the duration of cryostorage on clinical outcomes after embryo transfer of vitrified blastocysts stored in an open‐device slush‐nitrogen (SN 2 ) system. Methods A retrospective cohort study was carried out on 1632 autologous vitrified‐warmed blastocyst transfer cycles between January 2013 and June 2014. Duration of cryostorage was divided into four groups: Group I: 0–6 months (n=937); Group II: 7–12 months (n=299); Group III: 13–24 months (n=165); and Group IV: ≥25 months (n=231). The effects of the duration of cryostorage on the survival rate (SR), clinical pregnancy rate (CPR), live birth rate (LBR), and neonatal outcomes of vitrified blastocysts stored in an open‐device SN 2 system were evaluated. Results There were no significant differences between groups in SR, CPR, LBR, and neonatal outcomes after autologous vitrified‐warmed blastocyst transfer. Multivariate logistic regression analysis showed no effect on LBR from duration of cryostorage. Conclusion Vitrification using SN 2 and long‐term cryostorage in an open‐device system are safe and effective and do not significantly affect clinical outcomes after embryo transfer.