Fig. 1

Study Flow Chart. eSBET: elective single blastocyst-stage embryo transfer; MN2: multinucleation at the two-cell stage; 2MONO: non-multinucleated at the two-cells stage; 2BI1: binucleated at the two-cell stage in one blastomere; 2BI2: binucleated at the two-cell stage in both blastomere; 2MULTI1: true multinucleated at the two-cell stage in one blastomere; 2BI1/2MULTI1: binucleated in one blastomere and true multinucleated in the other blastomere at the two-cell stage; 2MULTI2: true multinucleated at the two-cell stage in both blastomeres; Group 1: the patients with no ≥ 3PN zygotes; Group 2: the patients with 0–25% ≥3PN zygotes; Group 3: the patients with more than 25% ≥3PN zygotes. The comparison of clinical outcomes included clinical pregnancy, ectopic pregnancy, ongoing pregnancy, and live birth rates.