Effects of vitrified cryopreservation duration on IVF and neonatal outcomes

Abstract

Background In this study, we aimed to evaluate the impact of the duration of cryopreservation storage on embryo viability, implantation competence, pregnancy outcome and neonatal outcomes. Methods We retrospectively evaluated the outcomes of patients who underwent IVF with vitrified cryopreserved embryos between January 2004 and August 2019 by following the first frozen embryo transfer cycles within the study period. A total of 31,143 patients met the inclusion criteria and were grouped according to the embryo storage time as follows: Group 1 (n = 20,926),1–90 days; Group 2 (n = 6,472), 91–180 days; Group 3 (n = 2,237), 181–365 days; Group 4 (n = 746), 366–730 days; and Group 5 (n = 762), > 731 days. Results The embryo survival rate decreased significantly with longer durations of cryopreservation. The highest and lowest survival rate was recorded in Group 1 and Group 5, respectively (34853/35338; 98.63% vs. 1281/1801; 71.13%; P < 0.01). The human chorionic gonadotropin (HCG) detection and clinical pregnancy rate was highest in Group 1 (57.85% and 55. 26%, respectively; P < 0.01). Short-term cryopreservation (≤ 3 months) is associated with higher rates of clinical pregnancy. There were no significant differences in neonatal birth weight, neonatal height and congenital anomalies among the groups (P > 0. 05). Conclusion The prolonged storage time of vitrified embryos negatively affected survival rate and clinical pregnancy rate. It did not have a significant influence on neonatal health. This study provides new findings about the relationship between prolonged storage time of vitrified embryos and clinical outcomes and offers evidence for the safety of using long-stored embryos after vitrification.

Effect of post-vitrification cryopreservation duration on singleton birth-weight in frozen-thawed blastocysts transfer cycles

“…The authors concluded that, although this group had the shortest GA (38.1 ± 1.7 weeks), it had little impact on neonatal health and that the blastocysts could be preserved for a long time post-vitrification. In a recent study involving 31,143 patients, the cryopreservation period did not affect neonatal birth-weight, but low birth-weight was not likely to occur after cryopreservation > 1 year, and the male-to-female ratio in the > 2-year cryopreservation group was significantly lower than that in several groups with a cryopreservation time of < 2 years ( 34 ). They suggested that this difference may be because patients in the longest cryopreserved period group were the oldest, and most of the embryos transferred were of poor quality.…”

Study on the optimal time limit of frozen embryo transfer and the effect of a long-term frozen embryo on pregnancy outcome

“…The embryo cryopreservation duration and its impact on pregnancy outcomes remain debated. Some studies [13,[29][30][31] suggest that the embryo cryopreservation duration does not significantly affect pregnancy outcomes, while others [32,33] indicate decreased survival and pregnancy rates with prolonged vitrification freezing. Our study shows that embryo cryopreservation duration for over 1 year specifically impairs pregnancy outcomes, consistent with the negative effects of extended freezing periods found in other studies.…”

Study on the optimal time limit of frozen embryo resuscitation transfer and the effect of a long-term frozen embryo on pregnancy outcome

“…The optimal timing for embryo freezing and its impact on pregnancy outcomes remain debated. Some studies 29,30,31,32 suggest that the duration of frozen time does not signi cantly affect pregnancy outcomes, while others 33,34 indicate decreased survival and pregnancy rates with prolonged vitri cation freezing. Our study shows that freezing embryos for over one year speci cally impairs pregnancy outcomes, consistent with the negative effects of extended freezing periods found in other studies.…”