ABSTRACT
Objective To analyze the phenomenon of monozygotictwin(MZT)in in vitro fertilization/intra-cytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET),and explore possible laboratory-related factors that may contribute to MZT. Methods Patients who transferred single embryo in our center from January 2015 to October 2016,including 1786 fresh embryo transfer cycles and 1710 thawed embryo transfer cycles and 49 preimplantation genetic diagnoses(PGD)cycles,were retrospectively analyzed. Correlation between fresh embryo,embryo freez-ing and thawing,embryo quality,artificial assistant hatching and MZT were analyzed. Results (1)There was no significant difference in the MZT rate between embryo age ,in vitro culturing time and in vitro fertilization mode (P > 0.05).(2)The MZT rate between fresh blastocysts and frozen-thawed blastocysts showed significant differ-ence(0.88%vs. 3.08%,P<0.05).(3)The incidence of MZT was significantly higher in laser hatching than that in mechanical hatching in PGD(25.00% vs. 0.00%,P < 0.05). Conclusion Frozen and assisted incubation of blastocyst are risk factors for MZT.