title: Day 3 embryo transfer with combined evaluation at the pronuclear and cleavage stages compares favourably with day 5 blastocyst transfer.
abstract: BACKGROUND
  The respective advantages of day 3 and day 5 embryo transfer are a matter of debate. Previous comparisons did not include pronuclear stage zygote scoring and cumulative success rates (fresh and cryopreserved embryos).
  
  
  METHODS
  Patients were randomized prospectively for day 3 or day 5 embryo transfer. Day 3 embryos were selected for transfer and cryopreservation by using combined evaluation at the pronuclear and cleavage stages.
  
  
  RESULTS
  There was no difference between day 3 and day 5 fresh embryo transfers as to the rates of pregnancy (58 versus 62%), clinical pregnancy (56 versus 58%), delivery (50 versus 48%), implantation (35 versus 38%) and birth (33 versus 36%) rates. The corresponding values for cryopreserved embryo transfers were also similar. However, day 3 embryo transfer compared favourably with day 5 transfer when the pregnancy (90 versus 66%), clinical pregnancy (85 versus 62%) and delivery (77 versus 52%) rates were calculated per oocyte recovery attempt.
  
  
  CONCLUSIONS
  With a selected population of good prognosis patients and our embryo selection criteria, the implantation potential of day 3 and day 5 embryos is equal. Per oocyte recovery attempt, day 3 transfer is more clinically efficient than day 5 transfer, but at least one transfer of cryopreserved embryos is necessary to manifest this superiority.
authors.affiliation: Reproductive Medicine, European Hospital, Via Portuense 700, 00149 Rome, Italy. rienzi.laura@libero.it
authors.forename: Laura
authors.initials: L
authors.lastname: Rienzi
authors.forename: Filippo
authors.initials: F
authors.lastname: Ubaldi
authors.forename: Marcello
authors.initials: M
authors.lastname: Iacobelli
authors.forename: Susanna
authors.initials: S
authors.lastname: Ferrero
authors.forename: Maria Giulia
authors.initials: MG
authors.lastname: Minasi
authors.forename: Francisco
authors.initials: F
authors.lastname: Martinez
authors.forename: Jan
authors.initials: J
authors.lastname: Tesarik
authors.forename: Ermanno
authors.initials: E
authors.lastname: Greco
mesh_terms: D000328:Adult; D001755:Blastocyst; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation; D036861:Delivery, Obstetric; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D009865:Oocytes; D036801:Parturition; D011247:Pregnancy; D018873:Pregnancy Rate; D013997:Time Factors; D020858:Tissue and Organ Harvesting; D017388:Zygote Intrafallopian Transfer