The study database includes all the single fresh and frozen (G5-G6) blastocyst transfers performed at Humanitas Fertility Centre between 1st January 2016 and 31th December 2021 by using the direct and afterload protocols.~Any blastocysts that underwent preimplantation genetic testing will be excluded from the analysis, as well as embryos derived from gamete donation or those imported from other centers.~Data are gathered using a specific internal web-based database, which allows to organize, store and readily retrieve information about patients and IVF cycle.
The primary outcome of the study is to determine if a difference in terms of pregnancy rate exists between direct and afterload embryo transfer (ET) techniques.~The secondary end points include the evaluation of the difficult transfer rates.