Abstract：
The use of frozen embryo transfer in assisted reproductive technology (ART) has steadily increased since development in the early 1980\'s. While there are many benefits to delayed frozen embryo transfer, certain adverse perinatal outcomes are noted to be more common in these transfers when compared to fresh transfers, specifically hypertensive disorders of pregnancy. Frozen embryo transfers require coordination between the embryo\'s developmental stage and the endometrial environment and can occur in either ovulatory or programmed cycles. Though there is no consensus on the ideal method of endometrial preparation prior to frozen embryo transfer, emerging data suggests differences in maternal and neonatal outcomes, specifically increased rates of hypertensive disorders of pregnancy in programmed cycles. Other reported differences include an increased risk of cesarean delivery, placenta accreta, postpartum hemorrhage, low birthweight, preterm birth, post term delivery, macrosomia, large for gestational age, and premature rupture of membranes in programmed cycles. The mechanism by which these differences exist could reflect inherent differences in groups selected for each type of endometrial preparation, the role of super physiologic hormone environments in programmed cycles, or the unique contributions of the corpus luteum in ovulatory cycles that are not present in programmed cycles. Given that existing studies are largely retrospective and have several key limitations, further investigation is needed. Confirmation of these findings has implications for current practice patterns and could enhance understanding of the mechanisms behind important adverse perinatal outcomes in those pursuing assisted reproduction.
摘要：
自1980年代早期发展以来，冷冻胚胎移植在辅助生殖技术（ART）中的使用一直在稳步增长。虽然延迟冷冻胚胎移植有很多好处，与新鲜转移相比，某些不良围产期结局在这些转移中更为常见，特别是妊娠高血压疾病。冷冻胚胎移植需要胚胎发育阶段和子宫内膜环境之间的协调，并且可以发生在排卵或编程周期中。尽管在冷冻胚胎移植前子宫内膜制备的理想方法尚未达成共识，新出现的数据表明，孕产妇和新生儿结局存在差异，在程序周期中妊娠高血压疾病的发生率特别增加。其他报告的差异包括剖宫产的风险增加，胎盘植入,产后出血,低出生体重,早产,后期交付，巨大儿,大的胎龄，和程序周期中的胎膜过早破裂。这些差异存在的机制可以反映为每种类型的子宫内膜准备所选择的组的固有差异。超生理激素环境在编程周期中的作用，或黄体在排卵周期中的独特贡献不存在于编程周期中。鉴于现有研究在很大程度上是回顾性的，并且有几个关键的局限性，需要进一步调查。这些发现的确认对当前的实践模式具有意义，并且可以增强对追求辅助生殖的人的重要不良围产期结局背后的机制的理解。
