Purpose

This systematic review and meta-analysis aimed to compare pregnancy outcomes between immediate frozen embryo transfer (FET) performed within the first menstrual cycle after oocyte retrieval and delayed FET following subsequent cycles.

Methods

PubMed, EMBASE, and Web of Science were searched for eligible studies through January 2020. The main outcome measures were clinical pregnancy rate (CPR), live birth rate (LBR), and pregnancy loss rate (PLR). The effect size was estimated as risk ratio (RR) with 95% confidence interval (CI) using a random effects model. Inter-study heterogeneity was assessed by the I² statistic.

Results

Twelve retrospective cohort studies involving 18,230 cycles were included. The pooled results revealed no significant differences between delayed and immediate FET in CPR (RR 0.94, 95% CI 0.87–1.03; I² = 67.9%), LBR (RR 0.94, 95% CI 0.85–1.03; I² = 67.5%), and PLR (RR 1.05, 95% CI 0.87–1.26; I² = 42.7%). Subgroup analyses of freeze-all cycles showed a marginal decrease of CPR in delayed FET (RR 0.93, 95% CI 0.86–1.00; I² = 53.6%), but no significant changes were observed regarding LBR (RR 0.93, 95% CI 0.85–1.02; I² = 65.2%) and PLR (RR 1.09, 95% CI 0.84–1.41; I² = 59.1%). No statistical differences were found in effect estimates among other subgroup analyses by ovarian stimulation protocol, trigger agent, endometrial preparation regimen, and embryo stage.

Conclusion

Timing of the first FET after oocyte retrieval was not significantly associated with pregnancy outcomes. This finding refutes the current common practice to delay FET after oocyte retrieval and reassures patients who wish to proceed with FET at their earliest convenience. Due to the high heterogeneity and observational nature of included studies, further randomized controlled trials are needed to confirm the results.

中文翻译：

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取卵后延迟与立即冷冻胚胎移植：系统评价和荟萃分析。

目的

本系统评价和荟萃分析旨在比较取卵后第一个月经周期内立即冷冻胚胎移植 (FET) 和后续周期延迟 FET 之间的妊娠结局。

方法

在 PubMed、EMBASE 和 Web of Science 中搜索到 2020 年 1 月的符合条件的研究。主要结果指标是临床妊娠率 (CPR)、活产率 (LBR) 和流产率 (PLR)。使用随机效应模型将效应大小估计为具有 95% 置信区间 (CI) 的风险比 (RR)。研究间异质性通过I ²统计量进行评估。

结果

包括 12 项回顾性队列研究，涉及 18,230 个周期。汇总结果显示延迟和即刻 FET 在 CPR (RR 0.94, 95% CI 0.87–1.03; I ²  = 67.9%)、LBR (RR 0.94, 95% CI 0.85–1.03; I ²  = 67.5%) 方面没有显着差异和 PLR（RR 1.05，95% CI 0.87–1.26；I ²  = 42.7%）。全冻结周期的亚组分析显示延迟 FET 的 CPR 略有下降（RR 0.93，95% CI 0.86–1.00；I ²  = 53.6%），但未观察到 LBR 的显着变化（RR 0.93，95% CI 0.85 –1.02；I ²  = 65.2%）和 PLR（RR 1.09，95% CI 0.84–1.41；I ² = 59.1%）。在通过卵巢刺激方案、触发剂、子宫内膜准备方案和胚胎阶段进行的其他亚组分析中，在效果估计方面没有发现统计学差异。

结论

取卵后第一次 FET 的时间与妊娠结局没有显着相关性。这一发现反驳了目前在取卵后延迟 FET 的普遍做法，并使希望尽早进行 FET 的患者放心。由于纳入研究的高度异质性和观察性，需要进一步的随机对照试验来证实结果。