Blastomere multinucleation: Contributing factors and effects on embryo development and clinical outcome

The aim of the study was to discover which intracytoplasmic sperm injection (ICSI) cycle parameters could influence the presence of multinucleated blastomeres (MNBs) and how ICSI outcomes are influenced by this event.

Embryos derived from normally fertilised oocytes were divided into two groups: embryos that had only mononucleated blastomeres (NBs group n = 2818) and embryos that had at least one multinucleated blastomere (MNB group, n = 404). The effects of ICSI cycle factors on multinucleation were investigated and embryo development was compared between the groups. The cycles were also split into those in which only NB embryos were present (NB cycles, n = 298) and cycles in which MNB embryos were present (MNB cycles, n = 203). ICSI outcomes were compared between the groups.

A higher incidence of MNB embryos arose in pituitary blockage with gonadotropin-releasing hormone agonists, male factor infertility and in cycles with higher number of retrieved oocytes. Embryos that had only one affected blastomere showed greater development than embryos with more than one affected blastomere. Finally, the implantation rate decreased when MNB embryos were transferred.

Multinucleation events may be affected by aspects of the ICSI cycle and compromise embryo quality and implantation rate.