Assessment of early cleaving in vitro fertilized human embryos at the 2-cell stage before transfer improves embryo selection

Objective: To determine the most viable embryos for transfer. Design: Study 1: Preselection of early-cleaving 2-cell embryos for transfer. Study 2: Alternating weeks during which preselection was performed and not performed. Setting: ART program, Birmingham Women's Hospital, Birmingham, United Kingdom. Patient(s): Patients undergoing IVF or ICSI cycles with transfer on day 2. Intervention(s): Culture of all fertilized embryos. Main Outcome Measure(s): Number of fertilized embryos cleaving to the 2-cell stage on day 1, embryo quality, implantation rates, and pregnancy rates. Result(s): Patients with early-cleaving 2-cell embryos had significantly higher pregnancy and implantation rates (45 of 100 [45.0%] and 58 of 219 [25.5%], respectively) than did patients without early-cleaving 2-cell embryos (31 of 130 [23.8%] and 43 of 290 [14.8%], respectively). In weeks during which preselection was used. the overall pregnancy and implantation rates of the clinic improved. Conclusion(s): The presence of early-cleaving 2-cell embryos improves a patient's chance of achieving pregnancy. Use of more stringent embryo selection criteria can improve overall pregnancy rates. (Fertil Steril (R) 2001-,76:1150-6. (C) 2001 by American Society for Reproductive Medicine.).