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Research question <p>Does administering progesterone for 6 days prior to frozen embryo transfer (FET) improve live birth rate (LBR) compared to 5 days of progesterone exposure when transferring blastocysts expanded on Day 6 (D6)?</p> Methods <p>This multicenter retrospective cohort study included 1,639 single FET cycles using D6 blastocysts under hormone replacement therapy (HRT) between January 2018 and December 2023. Cycles were stratified by duration of progesterone priming: 6 days (P6 group, <i>n</i> = 1,122) or 5 days (P5 group, <i>n</i> = 517). The primary outcome was LBR; secondary outcomes included biochemical and clinical pregnancy rates, miscarriage rate, and neonatal outcomes (birth weight and gestational age at delivery). Generalized estimating equation (GEE) regression models were used to adjust for potential confounders. Subgroup analyses by PGT status and sensitivity analyses restricted to first FET cycles or good-quality blastocysts were also conducted.</p> Results <p>The P6 group demonstrated a significantly higher LBR than the P5 group (33.87% [380/1,122] vs. 24.95% [129/517]; <i>P</i> &lt; 0.001). After multivariable adjustment, the P6 regimen remained independently associated with increased LBR (adjusted odds ratio [aOR] 1.72; 95% CI 1.32–2.19; <i>P</i> &lt; 0.001). Biochemical pregnancy (51.96% vs. 37.72%; aOR 2.10; 95% CI 1.64–2.62) and clinical pregnancy rates (46.52% vs. 33.66%; aOR 1.94; 95% CI 1.50–2.47) were also significantly higher with 6 days of progesterone priming. No significant differences were observed in miscarriage rates or neonatal outcomes between groups. Sensitivity analyses including restriction to first FET cycles, good-quality blastocysts, or stratification by blastocyst ploidy status did not alter the primary findings.</p> Conclusion <p>Extending progesterone exposure to 6 days before FET is associated with a significantly higher live birth rate compared with a 5-day protocol in transfers of vitrified–thawed Day 6 blastocysts. These findings warrant confirmation in prospective, large-scale randomized controlled trials.</p> Clinical trial number <p>Not applicable</p>

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Duration of progesterone exposure before frozen embryo transfer impacts live birth rates following single vitrified-thawed day 6 blastocyst transfer: a multicenter cohort study

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月28日

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  • He Cai,
  • Zhiqiang Wang,
  • Ying Fang,
  • Zan Shi,
  • Danmeng Liu,
  • Xiaokui Yang,
  • Yali Ni,
  • Juanzi Shi

摘要

Research question

Does administering progesterone for 6 days prior to frozen embryo transfer (FET) improve live birth rate (LBR) compared to 5 days of progesterone exposure when transferring blastocysts expanded on Day 6 (D6)?

Methods

This multicenter retrospective cohort study included 1,639 single FET cycles using D6 blastocysts under hormone replacement therapy (HRT) between January 2018 and December 2023. Cycles were stratified by duration of progesterone priming: 6 days (P6 group, n = 1,122) or 5 days (P5 group, n = 517). The primary outcome was LBR; secondary outcomes included biochemical and clinical pregnancy rates, miscarriage rate, and neonatal outcomes (birth weight and gestational age at delivery). Generalized estimating equation (GEE) regression models were used to adjust for potential confounders. Subgroup analyses by PGT status and sensitivity analyses restricted to first FET cycles or good-quality blastocysts were also conducted.

Results

The P6 group demonstrated a significantly higher LBR than the P5 group (33.87% [380/1,122] vs. 24.95% [129/517]; P < 0.001). After multivariable adjustment, the P6 regimen remained independently associated with increased LBR (adjusted odds ratio [aOR] 1.72; 95% CI 1.32–2.19; P < 0.001). Biochemical pregnancy (51.96% vs. 37.72%; aOR 2.10; 95% CI 1.64–2.62) and clinical pregnancy rates (46.52% vs. 33.66%; aOR 1.94; 95% CI 1.50–2.47) were also significantly higher with 6 days of progesterone priming. No significant differences were observed in miscarriage rates or neonatal outcomes between groups. Sensitivity analyses including restriction to first FET cycles, good-quality blastocysts, or stratification by blastocyst ploidy status did not alter the primary findings.

Conclusion

Extending progesterone exposure to 6 days before FET is associated with a significantly higher live birth rate compared with a 5-day protocol in transfers of vitrified–thawed Day 6 blastocysts. These findings warrant confirmation in prospective, large-scale randomized controlled trials.

Clinical trial number

Not applicable