title: The oocyte-to-baby rate of day 2, day 3 versus day 5 embryo transfer: a retrospective study.
abstract: OBJECTIVE
  To investigate whether the time of embryo transfer (ET) affect the oocyte-to-baby rate.
  
  
  METHODS
  The database was retrospectively analyzed including total number of oocytes collected and corresponding oocyte-to-live baby born (LBB) rate. Then the relationship between different time of embryo transfer and oocyte-to-baby rate was compared. In a year period all patients undergoing infertility treatment were included in the study. The outcome parameters were total number of oocytes collected and corresponding oocyte-to-LBB.
  
  
  RESULTS
  For patients under the age of 35 years, there was no increase in oocyte-to-LBB regardless of the time of ET. For patients older than 35 years, the oocyte use rate increased significantly when embryo was transferred on day 2. Oocyte-to-baby rates were also analyzed after grouping patients on the number of oocytes retrieved per cycle. For patients < 35 years, the oocyte- to -LBB rate increased significantly on day 3 if < ten oocytes were obtained. whereas for patients > 35 years, the oocyte-to-baby rate was best on day 2 when about 15 oocytes were retrieved.
  
  
  CONCLUSIONS
  This retrospective analysis demonstrated the relationship between the time of ET and ooctye-to-baby rate that is indicative of a more biologically efficient reproductive system.
authors.forename: H X
authors.initials: HX
authors.lastname: Wu
authors.forename: K M
authors.initials: KM
authors.lastname: Li
authors.forename: L
authors.initials: L
authors.lastname: Ai
authors.forename: J P
authors.initials: JP
authors.lastname: Pan
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: X M
authors.initials: XM
authors.lastname: Teng
mesh_terms: D000328:Adult; D000367:Age Factors; D015925:Cryopreservation; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D009865:Oocytes / Q000502:physiology*; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D013997:Time Factors