The rate of fragmentation in early cleaved embryos (25–27 h post insemination) alters implantation and pregnancy rates

Abstract

Assessment of early human embryo cleavage has proven a reliable parameter for embryo selection. The purpose of this retrospective study was to assess the effect of fragmentation in early cleaved embryos (25–27H post insemination) on day 2 -and day 3- embryo quality as well as on implantation and pregnancy rates. Retrospective study. A total of 1208 zygotes from 195 cIVF or ICSI cycles were graded 25–27 h post-insemination and classified into 3 groups according to the following parameters: group I = early cleaved embryos displaying 2 similar blastomeres; group II = uncleaved embryos with 0 PN and 2 PB; group III = uncleaved embryos with 2 PN and 2 PB. For group I only, the degree of fragmentation was also evaluated on day 1. Embryos were cultured in 30 μl drops of Vitrolife culture media under sterile mineral oil. From 1208 scored embryos : 406 (33.6%) early cleaved embryos were included in group I, 351 (29%) late cleaved embryos were classified in group II, and 451 (37.3%) in group III. In group I, 304 (85.9%) displayed 0 to 20% fragmentation, whereas 50 (14.1%) had more than 20% of fragmentation. On day 1, developmental arrest increased significantly in group I when fragmentation exceeded 20% (21.9% vs. 6.9% when less 10% fragmentation. On day 2, symmetrical embryos represented 58% of group I embryos with >20% fragmentation vs. 93.9% when fragmentation <10% (P<0.0001). Similar values were observed in group II, whereas the rate of symetrical embryos was significantly reduced (P<0.0001) in group III. Also, the number of blastomere per embryo on day 2 and day 3 was significantly higher in group I than in group III (Day 2: 4.2 vs. 3.1; day 3 : 7.15 vs. 5.44). Moreover, in group I, embryos with <10% fragmentation reached 7.25 blastomeres on day 3 vs. 6.44 when fragmentation was >20%. Early cleavage embryos from group I implanted at a two-fold higher rate than embryos from group III. The highest rate of implantation (34.5%) was obtained when 1 or 2 group I embryo with <20% fragmentation were transferred. The rate of implantation was only 19.2% in group III. Early cleavage of embryo associated with low fragmentation can be efficiently used as indicators of embryo viability. When embryos fill the criteria to enter both group I (early cleavage) and <20% fragmentation group, no more than 2 embryos should be transferred in order to reduce the risk of multiple pregnancies. The transfer of 2 or 3 embryos should be reconsidered with group III embryos only.