Twice vitrification-warming procedures has no effect on frozen-thawed embryo transfer outcomes
Abstract Background To evaluate the frozen-thawed embryo transfer (FET) outcomes of repeated cryopreservation by vitrification of blastocysts derived from vitrified-warmed day3 embryos in patients who experienced implantation failure previously. Methods We retrospect the files of patients who underwent single frozen-thawed blastocyst transfer cycles in our reproductive medical center from January 2013 to December 2019. 127 patients transfer of vitrified-warmed blastocysts derived from vitrified-warmed day3 embryos were defined as twice-cryopreserved group. 1567 patients who transfer blastocysts that had experienced once vitrified-warmed were used as once-cryopreserved group. None of them was pregnant at the previous FET. The outcomes were compared between two groups after a 1:1 propensity score matching (PSM). Results The clinical pregnancy rate was 52.76%, live birth rate was 43.31% in twice-cryopreserved group. After PSM,108 pairs of patients were generated for comparison. The clinical pregnancy rate, live birth rate or miscarriage rate was not significantly different between two groups. Logistic regression analysis indicated that double vitrification-warming procedures did not affect FET outcomes in terms of clinical pregnancy rate (OR 0.83, 95%CI 0.47-1.42), live birth rate (OR 0.93, 95%CI 0.54-1.59), miscarriage rate (OR 0.72 95%CI 0.28-1.85). Furthermore, the pregnancy complications rate, gestational age or neonatal abnormalities rate between two groups was also comparable, while twice vitrification-warming procedures might increase the macrosomia rate (19.6% vs. 6.3%, P = 0.05). Conclusion Transfer of double vitrified-warmed embryo at cleavage stage and subsequent blastocyst stage did not affect live birth rate and neonatal abnormalities rate, but there was a tendency to increase macrosomia rate, which needs further investigation.