Abstract: OBJECTIVE  To observe whether the optimal trigger day in in vitro fertilization/intra cytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) long protocol cycles is conformed to the "seven-five-three" odd number regular pattern by national distinguished master Xia Guicheng, as well as its effect on follicular and embryonic development and pregnancy outcome.METHODS  A total of 426 cases who underwent IVF/ICSI-ET for the first time due to female factor, they were divided into numerical trigger group and non-numerical trigger group according to whether the gonadotropin (Gn) initiation date to the trigger date conformed to the seven-five-three odd number regular pattern. In addition, we compared the Gn days, Gn dosage, egg acquisition rate, fertilization rate, 2 pronucleus (2 PN) rate, transferable embryo rate, clinical pregnancy rate, and live birth rate.RESULTS  ① The egg acquisition rate, 2PN rate, transferable embryo rate, clinical pregnancy rate and live birth rate of 186 cases in the seven-five-three odd number regular pattern trigger group were significantly higher than those in the non-numerical trigger group (P < 0.05, P < 0.01). ②As to "three" regular pattern subgroup, the fertilization rate was significantly higher in the numerical trigger group than that in the non-numerical trigger group (P < 0.01); As to "five" regular pattern subgroup, the Gn days and the total number of Gn in the numerical trigger group were significantly lower than those in the non-numerical trigger group (P < 0.01); The egg acquisition rate, embryo transferability rate and clinical pregnancy rate were significantly higher in the numerical trigger group than those in the non-numerical trigger group (P < 0.05, P < 0.01); As to "seven" regular pattern subgroup, the embryo transferability rate in the numerical trigger group was significantly higher than that in the non-numerical trigger group (P < 0.05).CONCLUSION  The seven-five-three odd number regular pattern proposed by Xia Guicheng, a national distinguished master, is applicable to the establishment of the trigger day of IVF/ICSI-ET long protocol cycle, and the transferable embryo rate can be improved by the seven and five regular pattern triggers. In addition, the five regular pattern trigger can increase the clinical pregnancy and live birth rates, and the three regular pattern trigger can increase the fertilization rate.