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.