Abstract: Objective：To explore those factors related to triploid zygotes in routine in vitro fertilization-embryo transfer (IVF-ET). Methods：To analyze retrospectively the clinical data of 1 987 IVF cycles. According to the 3PN rate, 1 987 IVF cycles were divided into three groups：normal group（3PN%=0, n=754）, the low frequency group（0＜3PN%＜20%, n=660） and the high frequency group（3PN%≥20 %, n=573）. Results：There were significant differences in the age of patients, the basal level of follicle stimulate hormone (FSH), days of Gn, the total ampoules of Gn, the progesterone level on the day of hCG administration, and sperm concentration after optimization (P＞0.05). The numbers of the retrieved oocytes and the maturated oocytes in both low and high frequency of 3PN groups were significantly higher than that in the normal group (P＜0.01). E2 levels on the day of hCG administration in those groups were also higher than that in the normal group (P＜0.05), while the ≥14 mm follicles rates on the day of hCG administration were significantly lower than that in the normal group(P＜0.01). It was sure that there was significant difference in the normal fertilization rate among the three groups(P＜0.01). The clinical pregnancy rates in the low frequency of 3PN group and the normal group had no statistical differences (P＞0.05), but were higher than the high frequency of 3PN group(P＜0.01). Interestingly, the sperm mobility rates after optimization in both low and high frequency of 3PN groups were significantly higher than that in the normal group, the rates of class a and b movement sperms were higher while the rates of class c and d movement sperms were lower in two groups than those in the normal group (P＜0.01), There were not significant differences in the rate of good quality embryo, the implantation rate and the abortion rate among three groups (P＞0.05). Conclusions：The higher level of estrogen on the day of hCG administration are positively associated with the occurrence of 3PN. The higher rate of ≥14 mm follicle by B ultrasound on the day of hCG administration, and the lower rate of living sperm after optimization, is negatively associated with the occurrence of 3PN. The higher rates of 3PN may affect the implantation rate and the clinical pregnancy rate.

Key words: Fertilization in vitro, Estradiol, Ovarian follicle, Spermatozoa, Embryo implantation, Pregnancy rate