Abstract: Objective：To analyze the clinical outcomes of different luteal support protocols in natural cycle frozen-thawed embryo transfer after hCG administration. Methods：A total of 286 patients aged ＜35 years undergoing the natural cycles and hCG induced ovulation, from January 2015 to January 2016, were randomly divided into three groups: the patients with no luteal support as the groupⅠ (n=81), the patients who received oral dydrogesterone as the groupⅡ (n=104), and the patients who received a combination of intramuscular progesterone and oral dydrogesterone as the group Ⅲ (n=101). The general data and clinical outcomes were compared among three groups. Results：There were no significant differences in the age, duration of infertility, types of infertility, causes of infertility, basic FSH level and BMI among the three groups (P＞0.05). There were no significant differences in the control ovarian hyperstimulation protocol, fertilization procedure, treatment outcomes of fresh cycle, hormone levels on the hCG day and endometrial thickness on the transfer day among the three groups (P＞0.05). Interestingly, there were no significant differences in the embryo recovery rate, implantation rate, clinical pregnancy rate, early abortion rate, ectopic pregnancy rate and continued pregnancy rate among the three groups (P＞0.05). Conclusions：It is feasible that there is no luteal support for those young patients undergoing hCG administration natural cycles, with a good communication. As for those patients who still have concerns, the protocol of oral dydrogesterone, with its convenience and curative effect, is advisable.

Key words: Embryo transfer, Fertilization in vitro, Chorionic gonadotropin, beta subunit, human, Corpus luteum, Frozen-thawed embryo transfer, Luteal support