Zhang J, et al. - In this retrospective cohort study of 2,664 patients with polycystic ovary syndrome (PCOS), researchers compared live birth rate (LBR) following frozen-thawed embryo transfer in letrozole-stimulated cycles vs artificial-cycle frozen-thawed embryos transfers. After statistical adjustment for confounding factors, higher LBR was noted in correlation to letrozole use for endometrial preparation compared with artificial cycles among patients with PCOS undergoing frozen embryo transfer.