Abstract: Objective：To investigate the correlation between serum vitamin D and the pregnancy outcome of in-vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) in women with polycystic ovary syndrome (PCOS). Methods: A total of 286 infertility women with PCOS underwent IVF/ICSI from November 2016 to June 2018 were included，including 114 women received fresh embryo transfer (ET). According to the level of 25-hydroxyvitamin D(25OHD), those patients were divided into three groups: vitamin D deficiency group (≤10 ng/mL), insufficiency group (10-30 ng/mL) and sufficiency group (≥30 ng/mL).The pregnancy rate of IVF/ICSI was analyzed. Furthermore, the patients with fresh ET were further divided into two groups: clinical pregnancy group and non-pregnancy group. After adjusting for baselines of luteinizing hormone (LH), testosterone and endometrial thickness on the ET day, logistic regression analysis on the vitamin D level and clinical pregnancy outcome of IVF/ICSI-ET was performed. Results: (1)There were significant differences in BMI, baseline testosterone, the ratio of baseline LH/FSH among three groups (P＜0.05). There were no significant differences in the indicators of ovulation induction (P＞0.05). (2)In those fresh ET patients, there were significant differences in BMI, the rate of fertilization and the rate of embryo implantation among three subgroups (P＜0.05). (3) The baselines of LH and testosterone in the pregnancy group were lower than those in the non-pregnancy group (P＜0.05), while the endometrial thickness on the ET day and the rate of fertilization in the pregnancy group were significantly higher than those in the non-pregnancy group (P＜0.05). After adjusting for age, baseline LH, baseline testosterone, the endometrial thickness on the ET day and the ratio of baseline LH/FSH, the logistic regression analysis showed that the pregnancy rates in the vitamin D insufficiency group and the sufficiency group were significantly higher than this rate in the vitamin D deficiency group （aOR=5.559，95%CI：1.463-21.124，P=0.012；aOR=11.192，95%CI：1.674-74.822，P=0.013）. Conclusions: The level of serum vitamin D≥10 ng/mL is a protective factor of IVF/ICSI-ET in women with PCOS.

Key words: Vitamin D；Polycystic ovary syndrome, Fertilization in vitro, Sperm injections, intracytoplasmic, Pregnancy outcome