The present study included data from PCOS couples underwent COS and IUI treatments at our center between January 1, 2016 and December 31, 2020. Clinical and demographic information were obtained from the medical archives. PCOS was diagnosed with the Rotterdam consensus.[3 ] The exclusion criteria were sperm anomality (the male factor), women with body mass index ≥ 30 kg/m2, endometriosis, obstruction of fallopian tube, and uterine or pelvic anomaly demonstrated either by hysterosalpingography or hysteroscopy. As depicted in the flowchart of Figure 1, a total of 404 cycles of COS and IUI treatments were finally enrolled, and divided into 2 groups according to the regime of trigger, that is the dual-trigger group (GnRH-a plus HCG, n = 109) and the HCG-only group (n = 295). Upon the first visit, each couple underwent a standard infertility workup in our center. For men, sperm analyses were performed after 3 to 5 days of sexual abstinence. For women, basal serum hormone measurements were conducted on day 3 to 5 of the menstrual cycle. This study was approved by The institutional ethics committee of our hospital (Approval number: 2015). Written informed consents were obtained from all the couples. This study was conducted according to the principles of the declaration of Helsinki.