DOES PROLONGED CRYOPRESERVATION AFFECT LIVE BIRTH RATES IN ELECTIVE FREEZE ALL CYCLES? - COGI 2023 The 31st World Congress on Controversies in Obstetrics, Gynecology & Infertility

Problem Statement

Does prolonged cryopreservation affect live birth rates in elective freeze all cycles?

Methods

A retrospective study of 655 consecutive women who underwent their first frozen embryo transfer cycle after vitrification of Day 5/ Day 6 Blastocysts in a private fertility center from January 2019 to December 2021 were included in this study. Duration of cryopreservation was categorized into five groups: G1 – 1 month (320 women), G2- 2-3 months (231 women), G3 – 4-6 months (75 women), G4- 7-12 months (21 women), G5- >12 months (9 women). Primary outcome measure was to compare Live birth rates (LBR) between the five groups. Secondary outcome measure was to compare the clinical pregnancy rate (CPR), blastocyst utilization rate and blastocyst survival rate between the five groups. Results were considered statistically significant when P<0.05 by comparison of proportions.

Results

LBR decreased with prolonged cryopreservation [G1- 64.86%, G2- 61.90% (P=0.0892), G3-50.66% (P =0.0029), G4 – 42.85% (P= 0.014) and G5 – 22.22% (P =0.0032). No difference in clinical pregnancy rates were seen between Group 1, 2, 3 and 4 and significant reduction was seen when in Group 5 (P= 0.004). Embryo utilization rate decreased with prolonged duration of cryopreservation (G1- 97.49%, G2- 94.15%, G3-85.81%, G4-74.28% and G5- 52.38%) which was all statistically significant (P< 0.0001). Similarly, blastocyst thaw survival rate also decreased with prolonged cryopreservation (G1- 100%, G2-99.35%, G3- 96.45%, G4-94.28% and G5-71.42%) and was found to be statistically significant (p< 0.001). Limitations of this study are; this was a retrospective, single center study. The sample size in Group 5 was very low, (9 women) when compared to other groups.

Conclusion

Women who opt for elective freeze all cycles, can be counseled to undergo an early FET (before 6 months of cryopreservation) as ART outcomes, embryo survival and utilization rates significantly decrease with prolonged cryopreservation.