Edinburgh Assisted Conception Programme, EFREC, Royal Infirmary of Edinburgh, 51 Little France Crescent, Old Dalkeith Road, Edinburgh, Scotland, EH164SA, UK.
ANDROFERT, Andrology and Human Reproduction Clinic, Campinas, Brazil; Department of Surgery (Division of Urology), University of Campinas (UNICAMP), Campinas, Brazil; Faculty of Health, Aarhus University, Aarhus, Denmark.
Cryobiology. 2020 Feb 1;92:9-14. doi: 10.1016/j.cryobiol.2019.11.041. Epub 2019 Nov 23.
A significant proportion of couples at reproductive age rely on assisted reproductive technology to overcome infertility. In vitro fertilisation (IVF) involves typically the use of exogenous gonadotropins to stimulate the ovary to produce oocytes, which are collected surgically. After fertilization by conventional IVF or intracytoplasmic sperm injection (ICSI), embryos are cultured in the embryology laboratory for a few days before being replaced into the uterus (fresh embryo transfer). Spare embryos can be vitrified and stored in liquid nitrogen to be transferred in a subsequent cycle. Over the years, concerns have arisen about possible adverse outcomes of transferring embryos back to the uterus immediately after controlled ovarian stimulation (COS) as regards to obstetrical and perinatal outcomes. It has been suggested that high hormonal levels during COS could create a relatively hostile environment for embryo implantation whilst increasing the risk of ovarian hyperstimulation syndrome (OHSS). With the remarkable improvement of vitrification as an alternative to the slow-freezing technique for human embryos, a new strategy the so-called "freeze-all" (FA) or "elective frozen embryo transfer" (eFET) was introduced. This approach involves COS, followed by the elective cryopreservation of the entire cohort of viable embryos to be transferred to the uterus in subsequent cycles in a possibly more physiological environment, thus avoiding the supra-physiologic hormonal levels observed during COS. The initial reports suggested that this policy could lead to improved pregnancy rates and reduced perinatal complications, which resulted in a steady increase and widespread use of FA globally. However, as data accumulated, it became clear that the use of FA to unselected couples undergoing ART offered no additional benefits over the conventional approach. Nonetheless, current evidence based on randomized controlled trials and observational studies indicates that FA might be justified in selected clinical scenarios, such as those involving the risk of OHSS. By contrast, there is a lack of evidence to support the FA policy for other indications, such as implantation failure or high progesterone levels on the trigger day. This review summarizes the clinical effectiveness of FA with the main focus on the health of offspring.
相当一部分育龄夫妇依赖辅助生殖技术来克服不孕不育。体外受精（IVF）通常涉及使用外源性促性腺激素刺激卵巢产生卵子，然后通过手术收集卵子。在常规 IVF 或胞浆内精子注射（ICSI）受精后，胚胎在胚胎学实验室中培养几天，然后再移植到子宫中（新鲜胚胎移植）。多余的胚胎可以进行玻璃化冷冻并储存在液氮中，以备后续周期移植。多年来，人们对控制性卵巢刺激（COS）后立即将胚胎移植回子宫对产科和围产期结局可能产生的不良后果表示担忧。有人认为，COS 期间的高激素水平可能会为胚胎着床创造一个相对不利的环境，同时增加卵巢过度刺激综合征（OHSS）的风险。随着玻璃化作为人类胚胎慢速冻技术的替代方法的显著改进，一种新的策略即所谓的“全部冷冻”（FA）或“选择性冷冻胚胎移植”（eFET）被引入。这种方法涉及 COS，随后选择冷冻保存整个可存活胚胎队列，以便在随后的周期中在可能更生理的环境中移植到子宫，从而避免在 COS 期间观察到的超生理激素水平。最初的报告表明，这种策略可以提高妊娠率并降低围产期并发症，从而导致全球范围内 FA 的使用稳步增加和广泛应用。然而，随着数据的积累，很明显，在未选择的接受 ART 的夫妇中使用 FA 并不能提供比传统方法更多的益处。尽管如此，目前基于随机对照试验和观察性研究的证据表明，FA 在某些特定临床情况下可能是合理的，例如存在 OHSS 风险的情况。相比之下，缺乏支持 FA 政策用于其他适应症的证据，例如着床失败或触发日孕激素水平升高。这篇综述总结了 FA 的临床效果，主要关注后代的健康。
