Spangmose AL, Ernstad EG, Malchau S, et al. - Researchers examined obstetric and perinatal outcomes in pregnancies after fresh blastocyst transfer (BT) vs those born after fresh cleavage stage transfer (CT) and spontaneous conception (SC). They conducted a retrospective register-based cohort study of data from Denmark, Norway and Sweden; three included cohorts comprised: 56,557 singletons and 16,315 twins born after fresh IVF/ICSI cycles and 2,808,323 SC singletons in Denmark (birth years 1997–2014), Norway (2010–2015) and Sweden (2002–2015). Among the fresh IVF/ICSI singletons, 4,601 were born after BT and 51,956 after CT. The twin cohort comprised 884 fresh IVF/ICSI children born after BT and 15,431 fresh IVF/ICSI children born after CT. They retrieved data from a large Nordic cohort of children born after ART and SC started by the Committee of Nordic ART and Safety (CoNARTaS). Analyses revealed a higher risk of placental and perinatal complications in correlation with fresh BT. Risk of placenta previa was higher in singleton pregnancies after BT vs CT. A higher risk of preterm birth was observed among singletons born after BT vs CT singletons, when estimated based on oocyte pick-up. Furthermore, they observed an altered male/female ratio with more males following BT vs CT. Higher risk of same-gender twins after single embryo transfer (SET) was observed after single BT vs single CT.