IRCT20180528039878N4 IRCT 2021-12-25 Mehr medical institute Sequential embryo transfer in repeated implantation failure The pregnancy outcome of sequential embryo transfer compared to blastocyst embryo transfer on patients with repeated implantation failure in frozen and thawed embryo transfer cycles-randomized clinical trial 2021-12-27 anticipated 200 Complete https://irct.ir/trial/60235 interventional Randomization: Randomized, Blinding: Not blinded, Placebo: Not used, Assignment: Parallel, Purpose: Other, Randomization description: Block randomization will be done using computer software. The list of blocks will be written and numbers will be assigned to them (AABB (1) - ABAB (2) -ABBA (3) -BBAA (4) - BABA (5) - BAAB (6)), then random numbers between one and six ( For example, 1 4 5, etc.) will be select and finally the treatment allocation list based on previous random numbers (AABB, BBAA, BABA, etc.) will be specified. 3 Repeated implantation failure. Intervention 1: Intervention group: In consecutive embryo transfer, first; 2 embryos of top and good quality will be transferred on day 2 or 3. The embryos will then be cultured to the blastocyst stage and 1 blastocyst will be transferred on day 5 or 6. Intervention 2: Control group: One to three blastocysts will be transferred on day 5 or 6. Undecided - It is not yet known if there will be a plan to make this available Justification or reason for indecision in sharing IPD is There is no further information.