Good quality blastocyst from non-/mono-pronuclear zygote may be used for transfer during IVF

Although healthy infants have developed from non- and mono-pronuclear zygotes, the transfer of embryos from non- and mono-pronuclear zygotes is not recommended because there are no proper selection criteria. In the present study, we discuss how to select non- and mono-pronuclear embryos with the highest developmental potential at 19–20 hours post-insemination. We found that the percentage of blastocysts with normal chromosome constitution in non-pronuclear zygotes was slightly higher than in mono-pronuclear zygotes. Non- and mono-pronuclear embryos that were at the 4-cell stage on D2 and/or at the 6- to 8-cell stage on D3 had higher incidence rates of blastocysts with normal chromosome constitutions. We also found higher incidences of blastocysts with normal chromosome constitution on D6 than on D5. The results suggest that if high quality non- and mono-pronuclear zygotes develop to the 4-cell stage on D2 and the 6-to 8- cell stages on D3, along with high quality D6 blastocysts, the incidence of blastocysts with normal chromosome constitution is higher.