Cleavage stage or blastocyst transfer: what are the benefits and harms?
Debate continues about the optimal day for embryo transfer--cleavage or blastocyst stage. There is a lack of good evidence about cumulative pregnancy outcomes after fresh and frozen-thawed transfers.
Volume 106, Issue 2, Pages 244-250
Demian Glujovsky, M.D., M.Sc., Cynthia Farquhar, M.D., M.P.H.
ET is a critical step in an assisted reproduction cycle. Over the past decade there has been an increasing trend to extending culture from cleavage-stage to blastocyst transfer. There has also been a trend to single ET and reporting the success of an assisted reproductive cycle as a cumulative live-birth rate after using both fresh and frozen embryos. There is low evidence that fresh blastocyst transfer is associated with improved live-birth rates compared with fresh cleavage-stage embryos. However, in the few studies that report cumulative pregnancy rates after fresh and frozen transfers, no significant difference was found. Cleavage-stage transfer is associated with greater numbers of embryos available for freezing, and blastocyst transfer is associated with increased number of cycles with no embryos to transfer. Further well-designed studies are warranted to evaluate the outcomes for blastocyst transfer including cumulative live-birth rate after fresh and frozen transfers, time to live birth, costs of the different transfer strategies, and perinatal mortality and severe perinatal morbidity.