Effect of the different fertilization time after human chorionic gonadotropin injection on the early embryonic development and clinical outcome of patients in in vitro fertilization-embryo transfer

Objective To investigate the effect of the different fertilization time after human chorionic gonadotropin (hCG) injection on the early embryonic development and clinical outcome of patients during in vitro fertilization-embryo transfer (IVF-ET). Methods A total of 200 patients undergoing IVF-ET were devided into 4 groups according to the different fertilization time after hCG injection. Group A: fertilization happened in 38.0-39.0 h after hCG injection, group B: 39.1-40.0 h after hCG injection, group C: 40.1-41.0 h after hCG injection, group D: 41.1-42.0 h after hCG injection, 50 cases in each group. The normal fertilization rate, cleavage rate, the high quality embryo rate, the embryo utilization rate, the clinical pregnancy rate, the implantation rate, and the spontaneous abortion rate were evaluated among the 4 groups. Results The embryo utiliazation rate in group B (65.7%), group C (63.3%), group D (66.8%) was higher than that of group A (55.5%) (P 0.05). Conclusion The different fertilization time after hCG injection in IVF-ET have effects on high-quality embryo rate. During a certain time range (38-42 h), as the increase of delayed fertilization time after hCG injection, high-quality embryo rate is also increasing. The best fertilization time of patients in IVF-ET was 40.1-41.0 h after hCG injection in our reproductive center, which can improve the clinical pregnancy rate, reduce the early abortion rate and get better clinical pregnancy outcome. Key words: Fertilization time;  In vitro fertilization-embryo transfer (IVF-ET); Human chorionic gonadotropin (hCG); Clinical pregnancy rate