title: Cleavage-stage or blastocyst transfer: what are the benefits and harms?
abstract: 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.
authors.affiliation: Department of Reproductive Medicine, Center of Studies of Genetics and Reproduction (CEGYR), Buenos Aires, Argentina.
authors.forename: Demián
authors.initials: D
authors.lastname: Glujovsky
authors.affiliation: Department of Obstetrics and Gynaecology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand. Electronic address: c.farquhar@auckland.ac.nz.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Farquhar
mesh_terms: D001755:Blastocyst / Q000473:pathology; D016009:Chi-Square Distribution; D002970:Cleavage Stage, Ovum / Q000473:pathology; D003362:Cost-Benefit Analysis; D015925:Cryopreservation; D046149:Embryo Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000009:adverse effects / Q000191:economics / Q000379:methods*; D005260:Female; D005298:Fertility; D005307:Fertilization in Vitro / Q000009:adverse effects / Q000191:economics; D017048:Health Care Costs; D006801:Humans; D007246:Infertility / Q000175:diagnosis / Q000191:economics / Q000503:physiopathology / Q000628:therapy*; D050498:Live Birth; D016017:Odds Ratio; D011247:Pregnancy; D018873:Pregnancy Rate; D018570:Risk Assessment; D012307:Risk Factors; D016896:Treatment Outcome
keywords: Embryo transfer; blastocyst; cleavage