Abstract: The midcycle surge of LH is absolutely required for the final maturation of oocyte，initiationof follicular rupture, and function of corpus luteum. Human chorionic gonadotrophin（hCG）and GnRH analogueare used for the final maturation of oocyte in assisted conception cycles. Which one is used usually depends onthe controlled ovarian stimulation （COS）protocol and different hypothalamus -pituitary condition. The timepoint, dose and medicine variety for trigger are dependent on the hypothalamus-pituitary condition, follicle andendometrium conditions of different protocols. hCG trigger induces better luteum function and high pregnancyrate, but it has higher OHSS rate. GnRH agonist causes low OHSS rate with the impaired pregnant andmiscarriage rate which could be improved by intensity luteum supply. GnRHa is not recommended to useroutinely asa trigger for final oocyte maturation in the fresh autologous cycles because of the lower ongoingpregnancy and live birth rates.

Key words: Luteinizing hormone, Chorionic gonadotropin, Gonadotropin -releasing hormone, Ovarian hyperstimulation syndrome, Ovulation induction