title: Is there any benefit from the culture of a single oocyte to a blastocyst-stage embryo in unstimulated cycles?
abstract: BACKGROUND
  The aim of the study was to test the influence of 2- and 5-day cultivation of a single oocyte on the pregnancy rate in a non-stimulated cycle.
  
  
  METHODS
  A retrospective chart review of 391 consecutive patients undergoing IVF and intracytoplasmic sperm injection in unstimulated cycles was performed. The embryos were kept in MediCult universal IVF medium for day 2 transfers and in BlastAssist System for day 5 transfers.
  
  
  RESULTS
  The oocyte recovery rate in the group for 2-day cultivation and in the group for 5-day cultivation was similar, being 79.4 (162/204) and 83.6% (154/187) respectively. The same is true of the fertilization rate (73.8 versus 77.7%). The blastulation rate was 52.8%. The embryo transfer rate per cycle was higher when day 2 embryos were transferred: 64.8% (105/162) compared with 35.7% (55/154) if blastocyst-stage embryos were transferred. The pregnancy rate per transferred embryo was higher when a blastocyst was transferred (40.0%) instead of a day 2 embryo (23.8%).
  
  
  CONCLUSIONS
  The expected pregnancy rate calculated per embryo available on day 2 of cultivation was similar in both groups (23.8 versus 22.2%) and it was not affected by oocyte culture to the blastocyst stage.
authors.affiliation: Department of Reproductive Medicine and Gynaecologic Endocrinology, Maribor Teaching Hospital, Ljubljanska 5, SI 2000 Maribor, Slovenia. vlai@sb-mb.si
authors.forename: V
authors.initials: V
authors.lastname: Vlaisavljević
authors.forename: B
authors.initials: B
authors.lastname: Kovacic
authors.forename: M
authors.initials: M
authors.lastname: Reljic
authors.forename: V G
authors.initials: VG
authors.lastname: Lovrec
authors.forename: M C
authors.initials: MC
authors.lastname: Sajko
mesh_terms: D001755:Blastocyst / Q000502:physiology*; D003470:Culture Media; D046508:Culture Techniques; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D009865:Oocytes / Q000502:physiology*; D011247:Pregnancy; D012189:Retrospective Studies; D020554:Sperm Injections, Intracytoplasmic; D013997:Time Factors
chemical_list: D003470:Culture Media