title: Freeze-all policy: is it time for that?
abstract: OBJECTIVE
  This publication will evaluate the available evidence in the literature comparing fresh embryo transfer (ET) and elective frozen-thawed embryo transfer (FET) regarding the possible interference of controlled ovarian stimulation (COS) in implantation and endometrial receptivity, IVF safety, and obstetric and perinatal outcomes.
  
  
  METHODS
  We performed a review in the literature of the available evidence comparing fresh to elective FET (freeze-all policy).
  
  
  RESULTS
  The improvements made in cryopreservation techniques have led to few or no detrimental effects to the embryo and have resulted in no consequences to the offspring when compared to fresh embryos; this has allowed reproductive practitioners to create the freeze-all policy (when all viable embryos are electively cryopreserved in the fresh cycle and transferred in a posterior cycle). There are increasing concerns about the adverse effects associated with COS over the endometrial and uterine environments, as well as with the safety of COS in pregnancies that have originated from fresh ET during in vitro fertilization (IVF) treatments. COS may contribute to modifications in the endometrium, which might be related to poorer outcomes when fresh ET is performed. It has been suggested that obstetric and perinatal outcomes in pregnancies resulting from fresh ET are poorer when compared with those that occur after FET. In cycles with fresh ET, there is still a risk of ovarian hyperstimulation syndrome (OHSS).
  
  
  CONCLUSIONS
  There is growing evidence in the literature suggesting better IVF outcomes, and decreased obstetric and perinatal morbidity when adopting the freeze-all policy instead of fresh ET.
authors.affiliation: ORIGEN - Center for Reproductive Medicine, Av Rodolfo de Amoedo, 140 - Barra da Tijuca, 22520-350, Rio de Janeiro, Rio de Janeiro, Brazil, matheusroque@hotmail.com.
authors.forename: Matheus
authors.initials: M
authors.lastname: Roque
mesh_terms: D015925:Cryopreservation / Q000191:economics / Q000379:methods*; D004624:Embryo Transfer / Q000379:methods*; D004622:Embryo, Mammalian; D004717:Endometrium / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects / Q000379:methods; D006801:Humans; D016471:Ovarian Hyperstimulation Syndrome / Q000209:etiology; D010062:Ovulation Induction / Q000379:methods*; D011247:Pregnancy; D018873:Pregnancy Rate; D019836:Preimplantation Diagnosis; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods; D016896:Treatment Outcome