Embryo selection by the first cleavage parameter between 25 and 27 hours after ICSI.

Purpose: The objective of this study was to assess first embryo cleavage (FEC) 25-27 h after intracytoplasmic sperm injection (ICSI) as a parameter for the embryo selection process. Methods: From January 1998 to December 1999, a total of 670 patients were subjected to the ICSI programme at the Centre for Human Reproduction, Sinha Junqueira Maternity Foundation, and the FEC parameter was evaluated in three situations. Results: In the first, a total of 300 zygotes were analyzed on the basis of a score (16-18 h after ICSI) and observed for the presence or absence of FEC (25-27 h after ICSI). A significant (p < 0.02) presence of FEC was observed in zygotes with a score of 15 (ideal score). In the second, a total of 200 patients were selected and divided into two groups matched for age and laboratory performance. Group I (n = 100) was subjected to transfer of embryos with the absence of FEC only (since in this cycle no embryos with FEC were detected within 25-27 h after ICSI) and Group II (n = 100) was subjected to transfer of embryos with the presence of FEC only. The age of Group 1 patients (33.8 ± 4.2 years) did not differ significantly (p = 0.50) from that of Group II patients (33.5 ± = 4.3 years). The number of embryos transferred was similar (p = 0.07) for Group I (2.7 ± 1.1) and Group II (2.9 ± 0.88). In Group II, the 17.5% implantation rate was significantly higher (p < 0.01) than the 5.9% rate obtained for Group I. The pregnancy rate for Group II was significantly higher (p < 0.01) (33%) than that for Group I (12%). The incidence of abortion was 16.6% in Group I as compared with 6% in Group II. In the third situation, we observed the frequency of embryos with FEC in 36 patients whose implantation rate was 100% (ideal result) and obtained a value of 82%. Conclusions: The data suggest that the presence of the FEC parameter that was evaluated 25-27 h after ICSI could be used to select embryos with a higher implantation power. The data reported here may justify routine analysis of embryos with FEC for the process of embryo selection after ICSI.