Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Jun 25:16:1551530.
doi: 10.3389/fendo.2025.1551530. eCollection 2025.

Analysis of factors influencing clinical pregnancy rates in frozen-thawed embryo transfer cycles

Junqiang Wang  1 , Zexing Yang  2 , Ying Chen  1   3 , Fengchen Gao  1 , Wenxiu Zhao  1 , Shuxuan Cao  1 , Yixi Li  1 , Limei He  1   3
Affiliations

Analysis of factors influencing clinical pregnancy rates in frozen-thawed embryo transfer cycles

Junqiang Wang et al. Front Endocrinol (Lausanne). .

Abstract

Objective: To identify the determinants influencing clinical pregnancy outcomes in frozen-thawed embryo transfer (FET) cycles.

Methods: A retrospective analysis was conducted on patients who underwent FET at the Department of Reproductive Genetics, The First Affiliated Hospital of Kunming Medical University, between January 2018 and December 2023. A total of 7,302 FET cycles were included and categorized into two groups based on clinical pregnancy outcomes: the clinical pregnancy group (n = 3,365) and the non-clinical pregnancy group (n = 3,937). Baseline characteristics were compared between groups. A random forest algorithm was applied to rank the importance of variables, followed by dimensionality reduction using a sliding window sequential forward selection (SWSFS) method. The top-ranked predictors with the lowest average out-of-bag (OOB) error rates were incorporated into a multivariate logistic regression model to determine independent predictors of clinical pregnancy in FET cycles.

Results: The overall clinical pregnancy rate (CPR) was 46.08%. The CPR was significantly higher in blastocyst transfers (61.14%) compared to cleavage-stage embryo transfers (34.13%) (χ² = 528.973, P < 0.01). The random forest model identified seven variables with the highest predictive value: female age, number of high-quality blastocysts, anti-Müllerian hormone (AMH) level, embryo stage at transfer, endometrial thickness on the day of transfer, number of high-quality cleavage-stage embryos, and pre-transfer endometrial thickness. Multivariate logistic regression analysis demonstrated that younger female age (OR: 0.93; 95% CI: 0.92-0.94), greater number of high-quality blastocysts (OR: 1.67; 95% CI: 1.49-1.88), higher AMH levels (OR: 1.03; 95% CI: 1.01-1.05), blastocyst transfer (OR: 2.31; 95% CI: 1.85-2.88), increased endometrial thickness on transfer day (OR: 1.10; 95% CI: 1.05-1.15), more high-quality cleavage-stage embryos (OR: 1.74; 95% CI: 1.59-1.92), and greater pre-transfer endometrial thickness (OR: 1.04; 95% CI: 1.00-1.09) were all independently associated with higher clinical pregnancy rates.

Conclusion: Female age, number of high-quality blastocysts, AMH levels, embryo stage at transfer, endometrial thickness on the day of transfer, number of high-quality cleavage-stage embryos, and pre-transfer endometrial thickness are significant predictors of clinical pregnancy outcomes in FET cycles. These findings may guide individualized embryo transfer strategies to optimize reproductive success.

Keywords: assisted reproductive technology; clinical pregnancy; female age; frozen-thawed embryo transfer; influencing factors.

PubMed Disclaimer

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Ranking of importance of factors influencing clinical pregnancy outcome.
Figure 2
Figure 2
Results of SWSFS analysis.
Figure 3
Figure 3
Forest plot of effects of factors influencing clinical pregnancy.
See this image and copyright information in PMC

Similar articles

See all similar articles

References

    1. Feng J, Wu Q, Liang Y, Liang Y, Bin Q. Epidemiological characteristics of infertility, 1990–2021, and 15-year forecasts: an analysis based on the global burden of disease study 2021. Reprod Health. (2025) 22:26. doi: 10.1186/s12978-025-01966-7 - DOI - PMC - PubMed
    1. Fauser BCJM, Adamson GD, Boivin J, Chambers GM, de Geyter C, Dyer S, et al. Declining global fertility rates and the implications for family planning and family building: an IFFS consensus document based on a narrative review of the literature. Hum Reprod Update. (2024) 30:153–73. doi: 10.1093/humupd/dmad028 - DOI - PMC - PubMed
    1. Chiware TM, Vermeulen N, Blondeel K, Farquharson R, Kiarie J, Lundin K, et al. IVF and other ART in low- and middle-income countries: a systematic landscape analysis. Hum Reprod Update. (2020) 27:213–28. doi: 10.1093/humupd/dmaa047 - DOI - PMC - PubMed
    1. Liu MF, Zhang F, Zhao H. Frontiers of reproductive health research (in Chinese). Sci Sin Vitae. (2024) 54:1–3. doi: 10.1360/SSV-2024-0010 - DOI
    1. Chang C-T, Weng S-F, Chuang H-Y, Hsu I-L, Hsu C-Y, Tsai E-M. Embryo transfer impact: a comprehensive national cohort analysis comparing maternal and neonatal outcomes across varied embryo stages in fresh and frozen transfers. Front Endocrinol. (2024) 15:1400255. doi: 10.3389/fendo.2024.1400255 - DOI - PMC - PubMed

LinkOut - more resources