The assosiation between preimplantation embryo morphology and the incidence of chromosome aneuploidy

Abstract

OBJECTIVE: To evaluate the association between preimplantation embryo morphology and proportion of aneuploidy on day 3 and 4 after oocyte retrieval. DESIGN: Retrospective analysis. MATERIALS AND METHODS: Preimplantation genetic screening (PGS) was performed in 64 IVF cycles of 58 patients because of history of repeated pregnancy loss, repeated implantation failure and advanced maternal age. The chromosomes 13, 16, 18, 21, X and Y were assessed in blastomeres biopysed from day 3 embryos by fluorescence in situ hybridization (FISH). A total of 614 embryos were analyzed. The incidence of chromosome aneuploidy was compared depending on the cell number, cellular fragment, and blastomere evenness of embryos. Data were analyzed by chi-square analysis. RESULTS: One hundred seventy-nine embryos (29.2%) were chromosomally normal and the others were aneuploid for one or more chromosomes. The incidence of aneuploidy was lower in normal-cleaving embryos (7- ∼ 9-cell stage) compared to slow-cleaving (≤ 6-cell stage) or fast-cleaving embryos (≥ 10-cell stage) at day 3 after oocytes retrieval. The incidence of aneuploidy was significantly higher (P<0.001) in slow-cleaving embryos (79.2%) than normal-cleaving embryos (62.0%). Aneuploidy of fast-cleaving embryos (78.6%) was higher than normal-cleaving embryos but there was no significant difference. The incidence of aneuploidy was significantly lower in normal-cleaving embryos (compaction ∼ morula stage, 58.9%) compared to arrested embryos (≤6-cell stage, 82.1%) or slow-cleaving embryos (7- ∼ 9-cell stage, 75.6%) at day 4 after oocytes retrieval. Aneuplody of moderately slow-cleaving embryos (10- ∼ 14-cell stage, 64.9%) was higher than normal-cleaving embryos but there was no significant. The incidence of chromosome aneuploidy was significantly increased (P<0.01) in embryos with cellular fragments more than 25% of embryo compared to embryos with cellular fragment less than 25% of embryo. Embryo with uneven blastomeres (73.7%) had a higher proportion of chromosome aneuploidy compared to those with even blastomeres (62.3%; P<0.01). CONCLUSIONS: The proportion of chromosome aneuploidy was significantly higher in slow-cleaving embryos compared to normal-cleaving embryos at day 3 and day4, respectively. The increase of cellular fragment and uneven blastomeres were associated with an increased incidence of chromosome abnormalities.