Comparison of the normal chromosome rate of embryos and the pregnancy rate between the blastocysts derived from 7-cell and 9-cell in preimplantation genetic diagnosis and screening

Objective To compare the normal chromosome rate of embryos and the pregnancy rate between the blastocyst derived from 7-cell and the blastocyst derived from 9-cell in preimplantation genetic diagnosis and screening (PGD/PGS) and to investigate the optimal division speed of embryos on day 3 of culture. Methods Retrospective analysis of 207 cycles with PGD/PGS in our hospital from April 1, 2014 to December 31, 2015 was conducted. The normal chromosome rate of embryos and the pregnancy rate were compared between the blastocyst derived from 7-cell and 9-cell. Results The rates of normal chromosomes between the blastocyst derived from 7-cell and 9-cell were 34.38% and 52.63%, respectively. There were statistical differences between them (χ2=4.100, P=0.042 9). The pregnancy rate between the blastocyst derived from 7-cell and 9-cell were 55.56% and 57.14%, respectively. There was no statistical difference between them (χ2=0.004, P>0.05). Conclusions The normal chromosome rate of the blastocysts derived from 9-cell was higher than that of the blastocyst derived from 7-cell in PGD/PGS. And similar clinical pregnancy rates can be achieved in the two types of blastocyst transferred in PGD/PGS. If the grading of the embryos were the same, the 9-cell embryos were superior to the 7-cell embryos on day 3 of culture. Key words: Preimplantation genetic diagnosis and screening (PGD/PGS); Blastocyst derived from 7-cell; Blastocyst derived from 9-cell; Blastocyst biopsy; Normal chromosome rate; Clinical pregnancy rate