STUDY QUESTION Does the change in endometrial thickness (EMT) from the end of the follicular/estrogen phase to the day of embryo transfer (ET) determine subsequent pregnancy outcomes? SUMMARY ANSWER Endometrial compaction from the late-proliferative to secretory phase is not associated with live birth rate (LBR) and other pregnancy outcomes. WHAT IS KNOWN ALREADY Endometrial compaction has been suggested to be indicative of endometrial responsiveness to progesterone, and its association with ET outcome has been investigated but is controversial. STUDY DESIGN, SIZE, DURATION A systematic review with meta-analysis was carried out. PubMed, EMBASE, and Web of Science were searched to identify relevant studies from inception to 18 November 2022. The reference lists of included studies were also manually screened for any additional publications. PARTICIPANTS/MATERIALS, SETTING, METHODS Cohort studies comparing ET pregnancy outcomes between patients with and without endometrial compaction were included. A review of the studies for inclusion, data extraction, and quality assessment was performed by two independent reviewers. The effect size was synthesized as odds ratio (OR) with 95% CI using a random-effects model. Heterogeneity and publication bias were assessed by the I2 statistic and Egger’s test, respectively. The primary outcome was LBR. Secondary outcomes included biochemical pregnancy rate (BPR), clinical pregnancy rate (CPR), miscarriage rate (MR), ongoing pregnancy rate (OPR), and ectopic pregnancy rate (EPR). MAIN RESULTS AND THE ROLE OF CHANCE Seventeen cohort studies involving 18 973 ET cycles fulfilled the eligibility criteria. The pooled results revealed that there were no significant differences between endometrial compaction and non-compaction groups in LBR (crude OR (cOR) = 0.95, 95% CI 0.87–1.04; I2 = 0%; adjusted OR (aOR) = 1.02, 95% CI 0.87–1.19, I2 = 79%), BPR (cOR = 0.93, 95% CI 0.81–1.06; I2 = 0%; aOR = 0.88, 95% CI 0.75–1.03, I2 = 0%), CPR (cOR = 0.98, 95% CI 0.81–1.18; I2 = 70%; aOR = 0.86, 95% CI 0.72–1.02, I2 = 13%), MR (cOR = 1.09, 95% CI 0.90–1.32; I2 = 0%; aOR = 0.91, 95% CI 0.64–1.31; I2 = 0%), and EPR (cOR = 0.70, 95% CI 0.31–1.61; I2 = 61%). The OPR was marginally higher in crude analysis (cOR = 1.48, 95% CI 1.01–2.16; I2 = 81%) among women with compacted endometrium, but was not evident in adjusted results (aOR = 1.36, 95% CI 0.86–2.14; I2 = 84%). Consistently, the pooled estimate of LBR remained comparable in further subgroup and sensitivity analyses according to the degree of compaction (0%, 5%, 10%, 15%, or 20%), type of ET (fresh, frozen, or euploid only), and endometrial preparation protocol (natural or artificial). No publication bias was observed based on Egger’s test. LIMITATIONS, REASONS FOR CAUTION Although the number of included studies is sufficient, data on certain measures, such as EPR, are limited. The inherent bias and residual confounding were also inevitable owing to the observational study design. Furthermore, inconsistent definitions of pregnancy outcomes may affect the accuracy of our pooled analysis. WIDER IMPLICATIONS OF THE FINDINGS Given the lack of prognostic value, assessing endometrial compaction or repeated EMT measurement on the day of ET may not be necessary or warranted. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by Natural Science Foundation of Jiangxi Province (20224BAB216025), National Natural Science Foundation of China (82260315), and Central Funds Guiding the Local Science and Technology Development (20221ZDG020071). The authors have no conflicts of interest to declare. REGISTRATION NUMBER CRD42022384539 (PROSPERO).

中文翻译：

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增殖至分泌型子宫内膜致密化与胚胎移植后妊娠结局之间的关联：系统评价和荟萃分析

研究问题 从卵泡/雌激素阶段结束到胚胎移植 (ET) 当天子宫内膜厚度 (EMT) 的变化是否决定随后的妊娠结局？摘要答案 子宫内膜从增殖后期到分泌期的致密程度与活产率 (LBR) 和其他妊娠结局无关。已知情况 子宫内膜致密性被认为是子宫内膜对黄体酮的反应性的指标，其与 ET 结果的关联已被研究，但存在争议。研究设计、规模、持续时间 通过荟萃分析进行了系统回顾。对 PubMed、EMBASE 和 Web of Science 进行了检索，以确定从开始到 2022 年 11 月 18 日的相关研究。纳入研究的参考文献列表也经过人工筛选，以查找任何其他出版物。参与者/材料、背景、方法 纳入了比较有和没有子宫内膜致密症患者的 ET 妊娠结局的队列研究。由两名独立评审员对研究的纳入、数据提取和质量评估进行评审。使用随机效应模型将效应大小合成为比值比 (OR)，CI 为 95%。异质性和发表偏倚分别通过 I2 统计和 Egger 检验进行评估。主要结局是 LBR。次要结局包括生化妊娠率（BPR）、临床妊娠率（CPR）、流产率（MR）、持续妊娠率（OPR）和异位妊娠率（EPR）。主要结果和机会的作用 涉及 18 973 个 ET 周期的 17 项队列研究符合资格标准。汇总结果显示，LBR 中子宫内膜致密化组和非致密化组之间没有显着差异（粗略 OR (cOR) = 0.95，95% CI 0.87–1.04；I2 = 0%；调整 OR (aOR) = 1.02，95 % CI 0.87–1.19，I2 = 79%），BPR（cOR = 0.93，95% CI 0.81–1.06；I2 = 0%；aOR = 0.88，95% CI 0.75–1.03，I2 = 0%），CPR（cOR = 0.98，95% CI 0.81–1.18；I2 = 70%；aOR = 0.86，95% CI 0.72–1.02，I2 = 13%），MR（cOR = 1.09，95% CI 0.90–1.32；I2 = 0%； aOR = 0.91，95% CI 0.64–1.31；I2 = 0%）和 EPR（cOR = 0.70，95% CI 0.31–1.61；I2 = 61%）。粗略分析中，子宫内膜致密的女性 OPR 略高（cOR = 1.48，95% CI 1.01–2.16；I2 = 81%），但在调整结果中并不明显（aOR = 1.36，95% CI 0.86–2.14；I2 = 81%）。 I2 = 84%）。一致地，根据压实程度（0％、5％、10％、15％或20％）、ET类型（新鲜、冷冻或仅整倍体），LBR的汇总估计在进一步的亚组和敏感性分析中保持可比性）和子宫内膜准备方案（天然或人工）。根据 Egger 的测试，没有观察到发表偏倚。局限性、谨慎理由 尽管纳入的研究数量充足，但某些措施（例如 EPR）的数据有限。由于观察性研究设计，固有的偏差和残留混杂因素也是不可避免的。此外，妊娠结局的不一致定义可能会影响我们汇总分析的准确性。研究结果的更广泛意义 鉴于缺乏预后价值，评估子宫内膜致密度或在 ET 当天重复进行 EMT 测量可能没有必要或没有必要。研究经费/竞争利益 这项工作得到了江西省自然科学基金 (20224BAB216025)、国家自然科学基金 (82260315) 和中央引导地方科技发展基金 (20221ZDG020071) 的支持。作者没有需要声明的利益冲突。注册号 CRD42022384539 (PROSPERO)。