Asserhøj LL, Spangmose AL, Henningsen AKA, et al. - Via performing this register-based cohort study, researchers examined if obstetric and perinatal outcomes in pregnancies differ by the type of frozen embryo transfer (FET) protocol. They assessed 1,136 singleton deliveries after frozen in vitro fertilization. Grouping of frozen embryo transfer cycles by type of FET protocol was done: programmed FET (n = 357); modified natural cycle FET (n = 611); and true natural cycle FET (n = 168). Outcomes revealed that programmed FET cycles adversely affect the obstetric and perinatal outcomes. Hence, they emphasize considering an endometrial preparation with the creation of a corpus luteum when possible.