Embryo multinucleation at the two-cell stage is an independent predictor of intracytoplasmic sperm injection outcomes.

OBJECTIVE: To determine the prognostic impact of the nuclear status at the two-cell stage on intracytoplasmic sperm injection (ICSI) outcomes. DESIGN: Retrospective study. SETTING: Hospital. PATIENT(S): Only ICSI cycles with time-lapse monitoring of transferred embryos with known implantation/delivery data from November 2012 to December 2014 were included. A total of 2,449 embryos were assessed for multinucleation rates at the two- and four-cell stage, and 608 transferred embryos were studied for ICSI outcomes. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Implantation rate (IR) and live birth rate (LBR) according to the number of multinucleated blastomeres at the two-cell stage: none (Without-MNB2cell), one (MNB1/2cell), and two (MNB2/2cell); morphokinetics of MNB2cell embryos. RESULT(S): Embryos with MNB1/2cell led to lower IR (27.7%) and LBR (22.7%) than embryos Without-MNB2cell (33.4% and 29.8%, respectively). The MNB2/2cell embryos led to significantly lower IR (18.3%) and LBR (13.4%) than embryos Without-MNB2cell. This difference remained significant in multivariate analysis for implantation (odds ratio 0.57; 95% confidence interval 0.34-0.94) and birth (odds ratio 0.46; 95% confidence interval 0.26-0.80), independently of the other significant parameters (women's age, time of two-cell formation, and multinucleation at the four-cell stage). Among implanted MNB2cell, if cleavage into four cells occurred later than 37 hours after insemination, embryos were significantly more likely to lead to birth. CONCLUSION(S): The presence of multinucleation at the two-cell stage and more specifically in both blastomeres had a significant negative impact on birth potential. Thus, embryo multinucleation at the two-cell stage should be used as an additional noninvasive criterion for embryo selection.