Abstract: Objective: To investigate the effect of the collected oocytes by controlled ovarian stimulation（COS, long GnRHa protocol) on the clinical outcomes of intracytoplasmic sperm injection（ICSI）. Methods：All couples （1 042 cycles） who underwent ICSI because of male factor were involved in this retrospective study，from January 2007 to June 2013 in our center. Those cycles were divided into 4 groups according to the number of collected oocytes: G1 as ≤4 oocytes（90 cycles），G2 as 5-10（368 cycles），G3 as 11-20 oocytes（449 cycles） and G4 as ≥21 oocytes（135 cycles）. Results：In the ICSI treatment cycle，the mean age in G1 was highest among 4 groups（P＜0.01），while 57.8% women were aged ＜35. The total fertilization failure（TFF） rate in G1, the ovarian hyperstimulation syndrome（OHSS） rate in G4 and the rates of cancelled transfer cycles in G1 and G4 were significantly higher than those in G2 and G3（P＜0.01）. The rate of clinical pregnancy in G1 was the lowest in 4 groups（31.3%，P＜0.05）. The rate of clinical pregnancy, the implant rate and the live birth rate in G3 were the highest in 4 groups（P＜0.05）. Conclusions：In the ICSI treatment cycle, the number of collected oocytes lower than 4 has negative effect on fertilization; the collected oocytes between 11 to 20 have good clinical outcomes.

Key words: Oocytes, Superovulation, Sperm injections, intracytoplasmic, Therapy