Abstract：
In contemporary times, the employment of vitrification freezing technology has led to the widespread adoption of frozen-thawed embryo transfer (FET) worldwide. Meanwhile, hormone replacement therapy (HRT) is a crucial protocol for priming the endometrium during FET cycles. Estrogen is required in HRT cycles for the induction of progesterone receptors and to promote endometrial thickness. However, there is no universal consensus on the treatment duration, dosage regimen, administration route, and target serum estrogen levels. Therefore, this study aimed to offer a comprehensive review of these topics. A shorter duration of estrogen exposure may elevate the risk of early miscarriage, while prolonged exposure to estrogen does not seem to confer advantages to general population and may be attempted in individuals with thin endometrium. Moreover, excessive estrogen levels on the day of progesterone administration may be associated with higher miscarriage rates and lower live birth rates (LBR). To offer more comprehensive guidance for clinical practice, extensive and prospective studies involving a large sample size are warranted to determine the optimal concentration and duration of estrogen exposure.
摘要：
在当代,玻璃化冷冻技术的应用导致冻融胚胎移植（FET）在全球范围内得到广泛采用。同时,激素替代疗法（HRT）是FET周期中启动子宫内膜的关键方案。在HRT周期中需要雌激素来诱导孕激素受体并促进子宫内膜厚度。然而,对治疗持续时间没有普遍共识，剂量方案，给药途径,和目标血清雌激素水平。因此,本研究旨在对这些主题进行全面回顾。较短的雌激素暴露时间可能会增加早期流产的风险，虽然长期暴露于雌激素似乎并不能给普通人群带来好处，并且可以在子宫内膜薄的个体中尝试。此外，孕酮给药当天雌激素水平过高可能与较高的流产率和较低的活产率(LBR)相关.为临床实践提供更全面的指导，有必要进行涉及大样本量的广泛和前瞻性研究,以确定雌激素暴露的最佳浓度和持续时间.
