title: Is it time for a paradigm shift in understanding embryo selection?
abstract: BACKGROUND
  Embryo selection has been an integral feature of in vitro fertilization (IVF) almost since its inception. Since the advent of extended blastocyst stage embryo culture, and especially with increasing popularity of elective single embryo transfer (eSET), the concept of embryo selection has increasingly become a mainstay of routine IVF.
  
  
  CONCLUSIONS
  We here, however, argue that embryo selection via blastocyst stage embryo transfer (BSET), as currently practiced, at best improves IVF outcomes only for a small minority of patients undergoing IVF cycles. For a large majority BSET is either ineffective or, indeed, may actually be harmful by decreasing IVF pregnancy chances. Overall, only a small minority of patients, thus, benefit from prolonged embryo culture, while BSET, as a tool to enhance IVF outcomes, is increasingly utilized as routine care in IVF for all patients.
  
  
  CONCLUSIONS
  Since newer methods of embryo selection, like preimplantation genetic screening (PGS) and closed system embryo incubation with time-lapse photography are practically dependent on BSET, these concepts of embryo selection, currently increasingly adopted in mainstream IVF, require reconsideration. They, automatically, transfer the downsides of BSET, including decreases in IVF pregnancy chances in some patients, to these new procedures, and in addition raise serious questions about cost-effectiveness.
authors.affiliation: The Center for Human Reproduction, 21 E 69th Street, New York, NY, USA. ngleicher@thechr.com.
authors.forename: Norbert
authors.initials: N
authors.lastname: Gleicher
authors.forename: Vitaly A
authors.initials: VA
authors.lastname: Kushnir
authors.forename: David H
authors.initials: DH
authors.lastname: Barad
mesh_terms: D001755:Blastocyst / Q000166:cytology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D019836:Preimplantation Diagnosis / Q000379:methods* / Q000706:statistics & numerical data; D011786:Quality Control; D056826:Single Embryo Transfer / Q000379:methods* / Q000592:standards