Standardization of Variable Conditions of Embryo Transfer Into the Uterine Cavity in the Procedure of Medically Assisted Procreation in Humans

The EFECT study is a clinical trial designed to determine whether improving the consistency of embryo transfer procedures can increase pregnancy success in patients undergoing frozen embryo transfer (cryoET). While laboratory techniques for fertilization, embryo culture, and selection have advanced significantly, the process of transferring embryos to the uterus remains variable and depends on small procedural differences, such as temperature changes, mechanical forces, timing, and individual operator techniques. These variations may affect embryo survival and implantation, ultimately influencing pregnancy outcomes. This study tests whether using specialized devices to standardize key aspects of embryo transfer-specifically temperature stability during transport and controlled, precise embryo aspiration and expulsion speed, optimal fluid volume, programmed injection time, elimination of pressure fluctuations and plunger backflow, prevention of embryo re-aspiration and detection of transfer catherer oclusion-can improve pregnancy rates. All embryos in the study are cultured using time-lapse monitoring and selected using artificial intelligence-supported grading, ensuring uniform quality for all participants. The study compares standard manual embryo transfer with transfer using one or both of the devices: Embryocase, which maintains a stable temperature during transport, and Embryopass, which standardizes the procedure and eliminates human factor. A total of 160 participants are randomly assigned to one of four groups: manual transfer without device support, manual transfer with Embryocase, transfer with Embryopass, or transfer with both devices. Participants and outcome assessors are blinded to group assignment, while the staff performing the transfer are aware due to the nature of the devices. All participants receive standard luteal phase support with progesterone following routine clinical practice. The study's main goal is to evaluate whether these procedural