title: Cryopreservation of blastocysts is the most feasible strategy in good responder patients.
abstract: OBJECTIVE
  To assess on which day to cryopreserve and transfer thawed embryos in good-responder patients by comparing the cycle outcomes of day 3 transfers vs blastocysts formed through extended culture before or after cryopreservation.
  
  
  METHODS
  Retrospective clinical study.
  
  
  METHODS
  Private IVF center.
  
  
  METHODS
  Frozen-thawed cycles (n = 2,531) who had ETs at day 3, 5, and 6 and post-thawed extended culture of day 3 until day 5 or 6.
  
  
  METHODS
  None.
  
  
  METHODS
  Primary outcomes were implantation and delivery rates. Secondary outcomes were clinical pregnancy and miscarriage rates.
  
  
  RESULTS
  In thawing cycles, embryos developing to blastocysts on day 5 through extended culture before or after cryopreservation yielded higher rates of implantation (51.1% and 51.3%, respectively), clinical pregnancy (69.9% and 62.2%, respectively), and delivery per thawing cycle (56.7% and 51%, respectively) accompanied by lower miscarriage rates (15.2%, 16.4%, respectively) compared with day 3 transfers (28.3%, 55.3%, 42.5%, 20.1%, respectively). Late-developing embryos formed before or after cryopreservation resulted in compromised implantation (44.7% and 44.2%, respectively), clinical pregnancy (59.9% and 45.9%, respectively), delivery per thawing cycle (42.8% and 32.4%, respectively) and higher miscarriage rates (25.7% and 23.5%, respectively) than day 5 embryos.
  
  
  CONCLUSIONS
  The feasible strategy in good responder patients appears to be the cryopreservation of blastocysts in the fresh cycle. Retardation in development results in a compromised outcome because of reduced inherent capacity of embryos.
authors: Bahceci Fulya IVF Center, Istanbul, Turkey.
authors: Nursen
authors: N
authors: Mesut
authors: Hadar Nadir
authors: HN
authors: Ciray
authors: Ali
authors: A
authors: Mesut
authors: Turan
authors: T
authors: Aksoy
authors: Mustafa
authors: M
authors: Bahceci
mesh_terms: D000022:Abortion, Spontaneous / Q000209:etiology; D000704:Analysis of Variance; D001755:Blastocyst; D016009:Chi-Square Distribution; D015925:Cryopreservation; D046149:Embryo Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000009:adverse effects; D005240:Feasibility Studies; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects; D006801:Humans; D007246:Infertility / Q000503:physiopathology / Q000628:therapy*; D050498:Live Birth; D054315:Oocyte Retrieval; D010062:Ovulation Induction; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D014421:Turkey