Zhang J, Wei M, Bian X, et al. - Researchers conducted this retrospective cohort study involving women with polycystic ovary syndrome (PCOS) who had undergone artificial frozen cycles or letrozole-stimulated frozen cycles with the aim to determine if and how letrozole use during frozen embryo transfer cycles affects obstetric and perinatal outcomes of singleton and twin pregnancies compared with artificial frozen cycles among women with PCOS. The final analysis was performed on a total of 2,427 women with PCOS. Among these, 1,168 women underwent artificial cycles and 1,259 women received letrozole treatment, of which 25% of women received letrozole alone and 75% of women received letrozole in combination with gonadotropins. Outcomes suggested a lower risk of hypertensive disorder of pregnancy in correlation with letrozole use for endometrial preparation in women with PCOS undergoing frozen embryo transfer compared with artificial cycles. Findings yielded a foundation that the raised risk of hypertensive disorder of pregnancy linked with frozen embryo transfer might be reduced by the utilization of physiological endometrial preparation protocols that result in the development of a corpus luteum, such as a mild ovarian stimulation cycle for oligo- or anovulatory women.