title: Use of the natural cycle and vitrification thawed blastocyst transfer results in better in-vitro fertilization outcomes : cycle regimens of vitrification thawed blastocyst transfer.
abstract: OBJECTIVE
  To compare the IVF outcomes of vitrification-thawed blastocyst transfer cycles utilizing different endometrial preparation methods.
  
  
  METHODS
  We retrospectively assessed IVF outcomes in 611 patients (648 cycles) who underwent blastocyst frozen embryo transfer (FET) between January 2007 and December 2009. All embryos had been cryopreserved by a vitrification method following a previous IVF cycle. Patients were prepared for transfer by using either the natural cycle (n = 310/Group 1), the natural cycle with ovulation induction employing human chorionic gonadotropin (n = 134/Group 2), or a hormonally manipulated artificial cycle with estrogen and progesterone supplementation (n = 204/Group 3).
  
  
  RESULTS
  Multivariate logistic regression analysis showed a significant difference in clinical pregnancy rate between Groups 3 (30.4%) and 1 (41.9%) (odds ratio [OR], 0.567; 95% confidence interval [CI], 0.379-0.847, P = 0.006) whereas the difference between Groups 2 and 1 was not significant (41.8% vs. 41.9%; OR, 0.683; 95% CI, 0.435-1.073; P = 0.098). Other significant variables affecting clinical pregnancy rate were the number of embryos transferred, the grade of transferred embryos, and maximal endometrial thickness.
  
  
  CONCLUSIONS
  The results showed that, using vitrification-thawed blastocyst transfer, employment of natural cycles with or without hCG treatment was associated with better outcomes than was the use of hormonally manipulated cycles.
authors.affiliation: Fertility Center of CHA General Hospital, Department of Obstetrics and Gynecology, College of Medicine, Pochon CHA University, 650-9 Yeoksam, Kangnamgu, Seoul, 135-081, Korea.
authors.forename: Eun Mi
authors.initials: EM
authors.lastname: Chang
authors.forename: Ji Eun
authors.initials: JE
authors.lastname: Han
authors.forename: You Shin
authors.initials: YS
authors.lastname: Kim
authors.forename: Sang Woo
authors.initials: SW
authors.lastname: Lyu
authors.forename: Woo Sik
authors.initials: WS
authors.lastname: Lee
authors.forename: Tae Ki
authors.initials: TK
authors.lastname: Yoon
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000378:metabolism; D018929:Cell Culture Techniques / Q000379:methods; D015925:Cryopreservation / Q000379:methods; D004624:Embryo Transfer; D005260:Female; D005306:Fertilization; D005307:Fertilization in Vitro; D006801:Humans; D016015:Logistic Models; D008597:Menstrual Cycle / Q000378:metabolism; D015999:Multivariate Analysis; D010062:Ovulation Induction / Q000379:methods; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D012189:Retrospective Studies; D058989:Vitrification