Early cleavage of human embryos to the two-cell stage. A simple, effective indicator of implantation and pregnancy in intracytoplasmic sperm injection.

Objective: To evaluate the relationship between embryo cleavage time and implantation and pregnancy rates in women undergoing intracytoplasmic sperm injection (ICSI) for male factor infertility.
Study Design: A total of 78 patients undergoing their first ICSI cycle were evaluated prospectively. Embryos were assessed for early cleavage to the two-cell stage 27 hours after injection.
Results: Early cleavage of at least one embryo was observed in 48 cycles (group I). None of the embryos cleaved early in the remaining 30 cycles (group II). There was no difference regarding mean patient age, duration of ovarian stimulation, number of gonadotropin ampules used, number of oocytes retrieved, fertilization, cleavage rates and embryo quality between the two groups. Implantation and clinical pregnancy rates were significantly higher in group I than II (17.9% and 45.8% vs. 5.1% and 16.7%, respectively; P < .05). Furthermore, progression to the blastocyst stage in excess embryos was significantly higher in group I than II (56.7% vs. 25.0%, P < .05).
Conclusion: Pregnancy and implantation rates were higher in patients who have early cleaving embryos; absence of early cleavage was associated with a poor outcome.