Abstract: Objective To study whether the increase of follicle-stimulating hormone/luteinizing hormone(FSH/LH) in the population with normal anti-müllerian hormone(AMH) is related to the occurrence of poor ovarian response(POR), in order to determine the diagnostic threshold. 
Methods A total of 4 363 cycles of patients undergoing in vitro fertilization-embryo transfer(IVF-ET) at the reproductive center of our hospital were analyzed. The relationship between FSH/LH and POR in the population with 1.1＜AMH＜6 μg/L was analyzed through the method of smooth curve fitting, to find the threshold or saturation point, based on which the population was grouped. The population characteristics, cycle information, and cycle outcome of the two groups were compared, and an increase in FSH/LH, and changes in POR and cycle outcome were analyzed. 
Results In the population with normal AMH, smooth cure fitting found that with the increase of FSH/LH level, the incidence of POR was increased, and the optimal saturation point was 3.3 by threshold and saturation analysis. By comparing FSH/LH＞3.3 group with FSH/LH＜3.3 group, age, body mass index(BMI), FSH, the starting dose of gonadotropins(Gn) and the total dose of Gn were significantly increased, whereas AMH, AFC, basal LH, E2, the total number of eggs obtained, the rate of transferable embryos, the E2 and P levels on the trigger day were all decreased(P＜0.05). 
Conclusion In the process of controlled ovarian hyperstimulation(COH), AMH is a reliable indicator to predict ovarian responsiveness. In the population with normal AMH, the incidence of POR increases with the increase of FSH/LH. FSH/LH:3.3 is a saturation value, but the accuracy of predicting the occurrence of POR is only 23%. In the population with elevated FSH/LH, both the increase of FSH and the decrease of LH are related to the occurrence of POR. The increase of FSH/LH reduces the final number of eggs obtained and the rate of transferable embryos, but does not affect the rate of high-quality embryos and the final pregnancy rate.  

Key words: embryo transfer, fertilization in vitro, poor ovarian response