GNRH1 and polycystic ovary syndrome: In 2020, one of them [19] randomized 343 patients with PCOS undergoing FET for endometrial preparation to or not to receive GnRH-a pretreatment, the results showed that the similar outcomes were found in implantation rate, clinical pregnancy rate and miscarriage rate between cases and controls, only with increased cost for patients with GnRH-a pretreatment.