title: Pregnancy rates following the exclusive transfer of twice frozen twice thawed embryos using a modified slow cool cryopreservation technique.
abstract: OBJECTIVE
  To determine the pregnancy rate following the exclusive transfer of twice frozen twice thawed embryos.
  
  
  METHODS
  All day 3 transfers of exclusive twice frozen-twice thawed embryos were retrospectively identified over a 13-year time-period. The cryopreservation technique used a simplified slow cool freezing protocol. Embryos could have been originally cryopreserved at the 2 pronuclear or multi-cell stage.
  
  
  RESULTS
  Survival rates were 83.3%. The live delivered pregnancy rate was 18.1% (15/83). The implantation rate was 13.1% (22/168).
  
  
  CONCLUSIONS
  These data suggest that twice frozen twice thawed embryos should not be discarded but either transferred alone if they are the only embryos left, or mixed with frozen embryos that have never been thawed. Though the live delivered pregnancy rates are inferior to fresh embryo transfer the marked reduction in cost and avoidance of the risk of ovarian hyperstimulation justifies their transfer.
authors.affiliation: Cooper Medical School of Rowan University, Department of Obstetrics and Gynecology Division of Reproductive Endocrinology & Infertility, Camden, NJ, USA. laurie@ccivf.com
authors.forename: J H
authors.initials: JH
authors.lastname: Check
authors.forename: D
authors.initials: D
authors.lastname: Summers-Chase
authors.forename: W
authors.initials: W
authors.lastname: Yuan
authors.forename: D
authors.initials: D
authors.lastname: Horwath
authors.forename: M C
authors.initials: MC
authors.lastname: Garberi-Levito
mesh_terms: D000328:Adult; D015925:Cryopreservation; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000502:physiology; D005260:Female; D005615:Freezing / Q000009:adverse effects; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies