Direct Unequal Cleavages: Embryo Developmental Competence, Genetic Constitution and Clinical Outcome

Abstract

ObjectiveTo investigate the prevalence, developmental potential, chromosomal constitution and clinical outcome of embryos with direct unequal cleavages (DUC).DesignA retrospective observational study.SettingAcademic Institution.Participant21,261 embryos from 3,155 cycles cultured in EmbryoScope®.ResultsThe total incidence of DUCs per embryo occupying the first three cleavages were 26.1%. Depending of the cell stage, DUC rate was 9.8% at first cleavage (DUC-1), 9.1% at second cleavage (DUC-2), and 3.7% at third cleavage (DUC-3) with 3.6% of embryos exhibiting multiple DUCs (DUC-Plus). The occurrence of DUCs was not correlated with female gamete age or source. The incidence of DUC-1 was significantly higher in embryos fertilized by epididymal and testicular sperm (13.6% and 11.4%, respectively) compared to ejaculated sperm (9.1%, all p<0.05). The total incidences of DUCs were strongly correlated with the onset of blastomere multinucleation (MNB) during the first three divisions. In MNB embryos, DUCs incidence are two to three times more likely to develop when compared to non-MNB embryos (OR = 3.11, 95% CI [2.64, 3.67] at 1-cell stage, OR = 2.64, 95% CI [2.39, 2.91] at 2-cell stage and OR = 2.51, 95% CI [1.84, 3.43] at 4-cell stage). The blastocyst formation rates gradually decreased from 61.0% in non-DUC to 40.2% in DUC-3, 18.8% in DUC-2, 8.2% in DUC-1 and 5.6% in multiple DUC embryos (DUC-Plus). The known implantation rates (FH) for day 3 (D3) transfers were 12.42% (n = 3172) in Non-DUC embryos, 6.3% (n = 127) in DUC-3, and 2.7% (n = 260) in DUC-2 embryos. No live births resulted from either DUC-1 (n = 225) or DUC-Plus (n = 100) embryo transfers. For blastocyst transfers, lower implantation rates (33.3%) but similar live birth (LB) rates (40%) were observed if DUC blastocysts were transferred. Comparatively rates in Non-DUC blastocyst were 45.2% and 34.8%, respectively. The euploid rate gradually increased from DUC-1, -2, -3 to Non-DUC (13.3%, 19.5%, 33.3%, 45.6%, p<0.001) for D3 biopsied embryos. Interestingly, the trend of decreased euploidy disappeared in DUC D5/6 biopsied embryos and similar rates were exemplified in DUC (D5 56.3%, D6 35.6%) vs. non-DUC (D5 51.4%, D6 33.8%) embryos.ConclusionBlastocyst formation, implantation potential and euploid rate were significantly reduced in DUC embryos. DUC embryos should be deselected for D3 transfers, but should be culture to blastocyst stage for possible ET.

Mosaicism in Preimplantation Human Embryos: When Chromosomal Abnormalities Are the Norm

“…Imaging of preimplantation embryos using both fixed- and live-cell microscopy supports a high frequency of multipolar mitosis during the cleavage stages, even for normally-fertilized 2PN zygotes [53, 54, 55]. The largest study to date, for example, observed that 26.1% of 21,261 2PN embryos exhibited tripolar mitosis [56], with previous studies obtaining similar, albeit slightly lower estimates (18% [54]; 17% [57]).…”

Cumulative live birth rates and perinatal outcomes with the use of time‐lapse imaging incubators for embryo culture: a retrospective cohort study of 1882 ART cycles

“…For SC cycles, embryo selection for transfer was done using morphological grading alone. In TLI cycles, embryo selection was primarily based on morphological grading with a secondary use of avoidance criteria, namely, uneven cell division at the two-cell stage, 13,14 multinucleation at the fourcell stage, 15,16 direct first cleavage from one to three cells [≤5 hours t3-t2 (t3, time for the embryo to reach 3 cell stage and t2, time to reach 2 cell stage)] 17,18 and irregular cleavage including reverse cleavage. 19 A urine pregnancy test was done 18 days after oocyte retrieval and an early pregnancy transvaginal ultrasound was done at approximately 7 weeks' gestation.…”

Timing of Embryo Cleavage

“…Zhan et al [11] defined as the abrupt cleavage of one blastomere into three daughter blastomeres or an interval of cell cycles less than 5 h. Therefore, they describe direct unequal cleavage at first cleavage as DUC-1, at second cleavage as DUC-2, at third cleavage as DUC-3 and embryos exhibiting multiple DUCs as DUC-Plus. They found that the embryos fertilized with the sperm from epididymis, and testicles have significant higher DUP-1 percentage (13.6 vs. 11.4%).…”