High proportion of zygotes with multiple pronuclei increase the embryo multinucleation rate during conventional IVF

The incidence of multiple pronuclei (≥ 3PN) zygotes and blastomere multinucleation was found to be elevated in the presence of increased estradiol (E 2 ) levels and a greater number of retrieved oocytes. This implies a potential link between the incidence of multinucleation at the two-cell stage (MN2) and a higher proportion of ≥ 3PN zygotes. We aimed to investigate the effect of high proportion of ≥ 3PN zygotes on MN2 incidence during conventional in vitro fertilization (C-IVF) by using time-lapse monitoring. This study included 1195 patients from January 2020 to December 2022. The patients were categorized into three groups: Group 1 comprised patients with no ≥ 3PN zygotes ( n = 422), Group 2 included those with 0–25% ≥3PN zygotes ( n = 617), and Group 3 consisted of patients with more than 25% ≥3PN zygotes ( n = 156). The MN2 rate, types of MN2 and clinical outcomes were compared among the three groups. Our data indicated that the MN2 rate was significantly lower in groups 1 and 2 compared to group 3 (18.33 versus 25.62%; p