Congenital anomaly and perinatal outcome following blastocyst- vs cleavage-stage embryo transfer: systematic review and network meta-analysis.

Current very-low certainty of evidence shows that there may be little-to-no difference in the risk for congenital anomaly or adverse perinatal outcome of pregnancy following blastocyst- vs cleavage-stage embryo transfer, although there was a slightly increased probability of a male neonate following blastocyst transfer. When considering cryopreservation, frozen-blastocyst transfer was associated with a reduction in the risk for LBW compared with both fresh-transfer modalities, and fresh-cleavage transfer may be associated with a reduction in the risk for perinatal death compared with frozen-blastocyst transfer. High-quality RCTs with separate data on fresh and frozen cycles and consistent reporting of culture conditions and freezing methods are mandatory. Individual participant data meta-analyses are required to address the substantial inconsistency resulting from current aggregate data approaches. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.