Introduction: Successful embryo implantation is a process which requires both a synchronous development and interaction between a hatched blastocyst and endometrium. After widespread application of assisted reproduction technologies (ART), a novel pathophysiological state is recognized which is characterized by numerous failures to achieve pregnancy after embryo transfer (ET) and it is designated as recurrent implantation failure (RIF) however there is no universally accepted definition despite many publications on this topic. RIF is failure to achieve pregnancy after ≥3 unsuccessful transfers of high quality embryos or transfers of ≥10 embryos in total in multiple transfers. RIF can be explained as a unique condition due to unidentified abnormalities or damage of the endometrium which would not even allow the initial steps of embryo implantation (apposition, attachment).
Aim of the work: The aim of the work was to study the impact of endometrial thickness change (endometrial compaction) after progesterone administration on pregnancy rate after frozen embryo transfer in multiple private centres.