title: Embryo quality in natural versus stimulated IVF cycles.
abstract: BACKGROUND
  The impact of controlled ovarian stimulation (COS) on oocyte and subsequent embryo quality remains controversial. In the present study we have compared embryo quality in natural and stimulated cycles in the same group of patients.
  
  
  METHODS
  This retrospective study was comprised of patients with a regular menstrual cycle who had IVF after COS using rFSH in a long GnRH agonist protocol. In all stimulated cycles the patients had fresh embryos transferred and surplus good quality embryos cryopreserved. Subsequently the same patients were treated with a modified FER cycle (mFER) where thawing of the frozen embryos was combined with aspiration of the dominant follicle in the natural cycle. The embryo cleavage stage and quality score were compared between the stimulated and the natural cycle for the patients having an embryo in the natural cycle.
  
  
  RESULTS
  In 177 cases patients returned for mFER in a natural cycle. Spontaneous ovulation had occurred in 35 cycles. In 17 cycles no oocyte was retrieved at aspiration and in 125 cycles 128 oocytes were aspirated. In the stimulated cycles from these patients we had obtained 950 embryos (cleavage rate 70.4%) versus 85 embryos (cleavage rate 66.4%) (P = 0.34) in the natural cycles. Comparing the embryos in the natural and stimulated cycles in all patients having an embryo in the natural cycle, we found no difference in the distribution between the different cleavage stages. Of the cleaved embryos, 53% in the stimulated cycles had >or=4 cells versus 59% in the natural cycles after 2 days culture (P = 0.31). In the stimulated cycles 61% of the embryos had <10% fragmentation at the time of transfer on day 2, compared to 69% in the natural cycles (P = 0.15).
  
  
  CONCLUSIONS
  The administration of exogenous gonadotrophins was not reflected in cleavage capacity or quality assessment of the resulting embryos.
authors.affiliation: The Fertility Clinic, Rigshospitalet, University Hospital of Copenhagen Section 4071, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. sziebe@rh.dk
authors.forename: S
authors.initials: S
authors.lastname: Ziebe
authors.forename: S
authors.initials: S
authors.lastname: Bangsbøll
authors.forename: K L T
authors.initials: KL
authors.lastname: Schmidt
authors.forename: A
authors.initials: A
authors.lastname: Loft
authors.forename: A
authors.initials: A
authors.lastname: Lindhard
authors.forename: A
authors.initials: A
authors.lastname: Nyboe Andersen
mesh_terms: D000328:Adult; D002970:Cleavage Stage, Ovum; D004334:Drug Administration Schedule; D004622:Embryo, Mammalian / Q000166:cytology* / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D005640:Follicle Stimulating Hormone / Q000627:therapeutic use; D007987:Gonadotropin-Releasing Hormone / Q000819:agonists; D006801:Humans; D008297:Male; D010062:Ovulation Induction; D011994:Recombinant Proteins / Q000627:therapeutic use; D012189:Retrospective Studies
chemical_list: D011994:Recombinant Proteins; D007987:Gonadotropin-Releasing Hormone; D005640:Follicle Stimulating Hormone