title: Successful pregnancy outcome after cryopreservation of all fresh embryos with subsequent transfer into an unstimulated cycle.
abstract: OBJECTIVE
  To assess the pregnancy outcome of freezing and storing all fresh embryos produced in a stimulated IVF cycle and replacing them in a subsequent nongonadotropin-stimulated cycle.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  University-associated assisted reproductive technology program.
  
  
  METHODS
  We studied 36 patients (age range 23 to 44 years) who underwent cryopreservation of all fresh embryos in a controlled ovarian hyperstimulation (COH) cycle because of either the risk of severe ovarian hyperstimulation (24 patients, group 1) or the presence of an endometrial lining < 8 mm in thickness (12 patients, group 2). Five hundred fifty-five embryos were generated for replacement in 63 cycles. All embryos were cryopreserved in 1.5 M propanediol at the pronuclear or two-cell stage, and 264 embryos subsequently were transferred into a hormone replacement cycle (70%) or natural ovulatory cycle (30%). The average number of embryos transferred per patient was 4.2.
  
  
  RESULTS
  Twenty-one clinical pregnancies were achieved, giving a pregnancy rate (PR) of 58.3% per patient (33.3% per cycle). The live birth rate was 50% per patient (28.6% per cycle). The implantation rate was 9.1%. Groups 1 and 2 had a similar PR per patient (58.3%). With 208 cryopreserved embryos remaining and considering the 33.3% PR per cycle, we expect the overall extrapolated PR to be 63.9%.
  
  
  CONCLUSIONS
  This is the first series showing that freezing and storing all fresh embryos produced in a stimulated IVF cycle and replacing them in a subsequent nongonadotropin-stimulated cycle results in successful PRs. These results underlie the importance of a successful cryopreservation program in IVF and could be a possible approach to overcoming the alleged adverse effects of COH on the endometrium, thereby improving the chances of pregnancy when numerous embryos are obtained simultaneously.
authors.affiliation: Department of Obstetrics and Gynecology, University of California, Irvine, Orange 92613-1491, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Frederick
authors.forename: T
authors.initials: T
authors.lastname: Ord
authors.forename: L M
authors.initials: LM
authors.lastname: Kettel
authors.forename: S C
authors.initials: SC
authors.lastname: Stone
authors.forename: J P
authors.initials: JP
authors.lastname: Balmaceda
authors.forename: R H
authors.initials: RH
authors.lastname: Asch
mesh_terms: D000328:Adult; D015925:Cryopreservation / Q000592:standards*; D004624:Embryo Transfer / Q000379:methods / Q000592:standards*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods; D006801:Humans; D008297:Male; D010060:Ovulation / Q000502:physiology*; D010062:Ovulation Induction; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D012189:Retrospective Studies