title: The number of eight-cell embryos is a key determinant for selecting day 3 or day 5 transfer.
abstract: OBJECTIVE
  To select patients for day 3 vs. day 5 embryo transfer.
  
  
  METHODS
  Retrospective analysis of assisted reproduction technology (ART) cycles comparing outcomes of day 3 and day 5 transfers.
  
  
  METHODS
  ART program of Brigham and Women's Hospital.
  
  
  METHODS
  Patients with day 3 or day 5 embryo transfers (n = 221 and 141, respectively).
  
  
  METHODS
  Cycles with eight or more zygotes were stratified by the number of eight-cell embryos available on day 3 (none, one or two, or three or more).
  
  
  METHODS
  Number of blastocysts, implantation rates, ongoing pregnancy rates, and number of fetal heart beats.
  
  
  RESULTS
  With no eight-cell embryos on day 3, 0% and 33% pregnancies resulted from day 5 vs. day 3 transfers. With one or two eight-cell embryos on day 3, ongoing and high order multiple rates were not different between day 3 and day 5 transfers. With three or more eight-cell embryos, day 5 transfer resulted in a decrease in multiple gestations but no difference in ongoing pregnancy rates compared with day 3 transfer.
  
  
  CONCLUSIONS
  With no eight-cell embryos on day 3, a day 3 transfer is warranted. With one or two eight-cell embryos, any benefit of day 5 transfer appears to be equivocal. With three or more eight-cell embryos, day 5 transfer is recommended.
authors.affiliation: Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. cracowsky@bics.bwh.harvard.edu
authors.forename: C
authors.initials: C
authors.lastname: Racowsky
authors.forename: K V
authors.initials: KV
authors.lastname: Jackson
authors.forename: N A
authors.initials: NA
authors.lastname: Cekleniak
authors.forename: J H
authors.initials: JH
authors.lastname: Fox
authors.forename: M D
authors.initials: MD
authors.lastname: Hornstein
authors.forename: E S
authors.initials: ES
authors.lastname: Ginsburg
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000166:cytology; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000379:methods*; D004622:Embryo, Mammalian / Q000166:cytology*; D005260:Female; D006801:Humans; D008423:Maternal Age; D011247:Pregnancy; D018873:Pregnancy Rate; D011272:Pregnancy, Multiple; D012189:Retrospective Studies; D013997:Time Factors