LAUSR

Abstract Purpose To study the relationship between clinical outcomes after assisted reproduction and the migration speed of nucleolus precursor bodies (NPBs) in male and female pronuclei (mPN; fPN). Methods NPB migration speed, embryo ploidy status, and live birth (LB) were retrospectively analyzed in IVF‐derived zygotes. The central coordinates of the mPN, fPN, and NPBs were noted at multiple timepoints. The migration distance of NPBs between two sequential images was measured to calculate NPB migration speed. Results The NPB migration speeds in mPN and fPN were significantly faster in euploid zygotes than in aneuploid zygotes. In multivariate logistic analysis, NPB migration speed in mPN and the female age were associated with euploidy. The NPB migration speeds in mPN and fPN were also significantly faster in zygotes that led to LB than in zygotes that led to no pregnancy. In a receiver operating characteristic curve analysis of LB by NPB migration speed in mPN, the cut‐off value was 3.74 μm/h (AUC: 0.825, 95%CI: 0.688–0.963). When the zygotes were categorized by this cut‐off value, there were significantly more LBs in zygotes with migration speed ≥ the cut‐off (78.9% vs. 21.1%). Conclusions Zygotes with quickly migrating NPBs demonstrated the developmental potential to become a baby.