Abstract: Objective：To analyze the clinical outcomes of the modified natural-cycle for ageing women with poor responder who failed to get pregnancy in the first in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) of minimal ovarian stimulation, and to discuss the treatment protocols of ageing women with poor ovarian reservation. Methods：This is a retrospective study. A total of 25 ageing women with poor ovarian reservation who failed to get pregnancy the first IVF/ICSI-ET cycle with minimal stimulation protocol were changed to the modified natural-cycle in our center from January 2016 to June 2017. The level of serum E2, the follicle size on the trigger day, the number of oocytes retrieved, the rate of oocyte maturation, the fertilization rate, the high quality embryos rate, and the clinical pregnancy rate, the miscarriage rate and the ectopic pregnancy rate were compared in the self-controlled design. Results：There were significant differences in the average diameter of follicle and the E2 level on the trigger day between the modified natural-cycle group and the minimal stimulation cycle group [(19.8±1.3) mm vs. (17.8±1.0) mm, (582.1±165.9) pmol/L vs. (681.4±99.1) pmol/L, both P＜0.05]. Although the number of oocytes retrieved in the modified natural-cycle group [(1.0±0.0) vs. (2.7±1.4)] was lower than that in the minimal stimulation cycle group, the rate of oocyte maturation (100%), the fertilization rate (100%) and the high quality embryos rate (80%) were significantly higher than that in the minimal stimulation cycle group (80.6%, 81.5% and 36.4%, all P＜0.05). Conclusions：The modified natural-cycle can make the almost same outcomes as the minimal stimulation cycle by the improved significantly quality of the embryo in those ageing women with poor ovarian reservation, although the number of oocytes retrieved was even lower in their modified natural-cycles.

Key words: Reproductive techniques, assisted, Ovulation induction, Poor ovarian responder, Modified natural-cycle