Study of nucleation status in the second cell cycle of human embryo and its impact on implantation rate

Aguilar, J, Rubio, I, Munoz, E, Pellicer, A, Meseguer, M,
Fertil Steril. Aug. 2016 doi: 10.1016/j.fertnstert.2016.03.036


OBJECTIVE: To study nucleation status in two- and four-cell embryos and its effect on reproductive outcomes. DESIGN: Retrospective cohort study. SETTING: University-affiliated private center. PATIENT(S): A total of 1,679 embryos from 940 oocyte donation cycles from May 2012 to May 2014. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Implantation, morphokinetics, and nucleation status restoration. RESULT(S): Multinucleation was present in 42.53% of embryos with known implantation data at the two-cell stage; it was present in approximately 14% of them at the four-cell stage. In all, 73.4% of the embryos were multinucleated at two cells and restored their nucleation status when they cleaved into four cells. Embryos with blastomeres multinucleated (more than two nuclei) at the four-cell stage showed a lower implantation rate. The average length of S-phase in the first embryo cell cycle in the positive known implantation data (KID+) embryos was longer than in KID- (15.50 hours vs. 14.38 hours) and slightly shorter in the second embryo cell cycle (8.35 hours in KID+ vs. 8.60 hours in KID-). CONCLUSION(S): Multinucleation in two-cell-stage embryos is a frequent event, which is reversible in a high proportion of embryos, without impact on the implantation rate; and embryos with multinucleated blastomeres have a reduced outcome compared with those with binucleated blastomeres when multinucleation is present in four-cell-stage embryos.