Early cleavage: an important evaluating indicator for selecting embryos to transfer

Abstract

Objective To investigate the impact of early cleavage (EC) on the outcomes of in vitro fertilization-embryo transfer (IVF-ET) and assess whether EC can be used as an additional parameter for day-3 embryo selection. Methods This retrospective cohort study included 267 fresh IVF-ET cycles. The transplanted embryos were day-3 high-quality embryos. According to the number of EC embryos in the transplanted embryos, they were divided into three groups: group A (two EC embryos), group B (one EC embryo and one non-EC embryo) and group C (two non-EC embryos). The differences of biochemical pregnancy rate, implantation rate, clinical pregnancy rate, spontaneous abortion rate, fraternal twins rate and live-birth rate were compared among the three groups. Results 1) There was no significant difference among the three groups in clinical and in vitro fertilization characteristics [i.e. female age, male age, infertility duration, ovarian stimulation protocol, egg number, MII egg number, fertilization rate, embryo quality and endometrial thickness on the day of human chorionic gonadotropin (hCG) injection] (P>0.05). 2) Compared with group B, group A had a lower biochemical pregnancy rate, and higher rates of implantation, clinical pregnancy and live-birth, but the differences were not statistically significant (P>0.05). 3) Compared with group C, group B had lower biochemical pregnancy rate and spontaneous abortion rate, and higher implantation rate, clinical pregnancy rate and live-birth rate, but the differences were not significant (P>0.05). 4) Compared with group C, the biochemical pregnancy rate and the spontaneous abortion rate in group A were lower but the implantation rate, the clinical pregnancy rate and the live-birth rate were higher, and the differences of biochemical pregnancy rate (1.3% vs 8.6%, χ2=4.665, P=0.031), implantation rate (42.3% vs 31.7%, χ2=4.315, P=0.038), clinical pregnancy rate (65.4% vs 49.0%, χ2=4.834, P=0.028) and live-birth rate (51.3% vs 35.6%, χ2=4.504, P=0.034) were statistically significant. Conclusion Transfer of EC day-3 high-quality embryos can achieve higher implantation rate, clinical pregnancy rate and live-birth rate. Therefore, EC can be used as an important evaluating indicator for embryo selection in day-3 transfer. Key words: Early cleavage (EC); In vitro fertilization-embryo transfer (IVF-ET); Embryo selection; Pregnancy rate; Live-birth rate