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An all-37 °C thawing method improves the clinical outcomes of vitrified frozen-thawed embryo transfer: a retrospective study using a case–control matching analysis

  • Gynecologic Endocrinology and Reproductive Medicine
  • Published:
Archives of Gynecology and Obstetrics Aims and scope Submit manuscript

Abstract

Purpose

The purpose of this study is to assess the impact of different temperatures and incubation times on the clinical outcomes of FET cycles during the thawing procedure and to select a better thawing method to improve clinical outcomes.

Methods

This retrospective study included 1734 FET cycles from January 1, 2020, to January 30, 2022. Embryos vitrified using a KITAZATO Vitrification Kit were thawed at 37 °C in all steps (the case group, denoted the “all-37 °C” group) or at 37 °C and then at room temperature (RT; the control group, denoted the “37 °C-RT” group), according to the kit instructions. The groups were matched 1:1 to avoid confounding.

Results

After case–control matching, 366 all-37 °C cycles and 366 37 °C-RT cycles were included. The baseline characteristics were similar (all P > 0.05) between the two groups after matching. FET of the all-37 °C group yielded a higher clinical pregnancy rate (CPR; P = 0.009) and implantation rate (IR; P = 0.019) than FET of the 37 °C-RT group. For blastocyst transfers, the CPR (P = 0.019) and IR (P = 0.025) were significantly higher in the all-37 °C group than in the 37 °C-RT group. For D3-embryo transfers, the CPR and IR were non-significantly higher in the all-37 °C group than in the 37 °C-RT group (P > 0.05).

Conclusions

Thawing vitrified embryos at 37 °C in all steps with shortening wash time can enhance CPR and IR in FET cycles. Well-designed prospective studies are warranted to further evaluate the efficacy and safety of the all-37 °C thawing method.

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Data availability

The authors confirm that the data supporting the finding of this study are available within the article.

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Funding

This study was supported by Kunming Medical University (No. CXTD202105).

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Author notes

  1. Gaofeng Yan and Youlin Yao contributed equally to this work.

Authors and Affiliations

  1. Department of Reproduction and Genetics, First Affiliated Hospital of Kunming Medical University, Kunming, 650032, Yunnan, China

    Gaofeng Yan, Youlin Yao, Wenjuan Yang, Ling Lu, Longda Wang, Di Zhao & Shuhua Zhao

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  1. Gaofeng Yan
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  2. Youlin Yao
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  3. Wenjuan Yang
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Contributions

SZ, GY, and YY designed the study. WY, LL, LW, and DZ collected the data. SZ and GY performed the data analyses and wrote the manuscript. All authors approved the final manuscript.

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Correspondence to Shuhua Zhao.

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The authors declare no competing interests.

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This study was conducted according to the Declaration of Helsinki and approved by the Ethics Committee of the First Affiliated Hospital of Kunming Medical University, and no informed consent was required because the study was a retrospective study.

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Yan, G., Yao, Y., Yang, W. et al. An all-37 °C thawing method improves the clinical outcomes of vitrified frozen-thawed embryo transfer: a retrospective study using a case–control matching analysis. Arch Gynecol Obstet 307, 1991–1999 (2023). https://doi.org/10.1007/s00404-023-07029-1

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