Early-cleavage is a reliable predictor for embryo implantation in the GnRH agonist protocols but not in the GnRH antagonist protocols

This retrospective study included 534 patients undergoing a fresh cycle of oocyte retrieval and the day-3 embryo transfer (from 22 to 46 years old). Of the 534 patients treated, 331 received a GnRH agonist long stimulation protocol (GnRH agonist group) for ovarian stimulation and 203 patients received a GnRH antagonist protocol (GnRH antagonist group). In each group, patients who had at least one early-cleavage embryo transferred were designated as the 'early-cleavage' subgroup. Patients who had no early-cleavage embryos transferred were designated as the 'late-cleavage' subgroup.The early cleavage rate was significantly lower in the GnRH antagonist group compared with that in the GnRH agonist group (IVF cycles: 34% versus 20%; ICSI cycles: 50% versus 37.8%, respectively, P < 0.0001). In the GnRH agonist group, the pregnancy rates were significantly higher in the early-cleavage subgroup than those in the late-cleavage subgroup (53.7% vs 33.9%, P < 0.0001). In the GnRH antagonist group, the pregnancy rates were not significantly different between the early-cleavage and late-cleavage subgroups (45.9% vs 43.8%, P > 0.05).Early cleavage of zygote is not a reliable predictor for embryo implantation potential in using the GnRH antagonist protocol. Furthermore, the implantation rates between the GnRH agonist and GnRH antagonist groups were comparable.In order to reduce multiple pregnancies and achieve a maximal rate of implantation, selection of the most viable embryo for transfer has become a high priority in assisted reproduction treatment. Traditionally, embryo selection is performed by using embryo morphology as the guideline. Other additional selection methods include oocyte and zygote morphology, blastomere symmetry and blastocyst culture. Recently, observation of embryonic first mitosis has been emphasized. Several studies have shown that embryonic early cleavage, which occurs at 25–27 hours post insemination for in vitro fertilization (IVF)/intracytoplasmic sperm i