title: Letrozole ovulation induction: an effective option in endometrial preparation for frozen-thawed embryo transfer.
abstract: OBJECTIVE
  To evaluate the clinical efficacy of letrozole on ovulation induction and hormone replacement therapy (HRT) during endometrial preparation for frozen-thawed embryo transfer (FET).
  
  
  METHODS
  We analyzed totally 1,230 cycles of patients that underwent FET from October 2010 to September 2012. Seven hundred and thirteen cycles of patients with ovulation disorders that underwent FET were randomly assigned to two groups by case control study. 359 cycles received letrozole ovulation induction and 354 cycles received HRT during endometrial preparation for FET, respectively. In the corresponding period, 517 cycles of patients with normal ovulation in the natural cycle group for FET endometrial preparation served as controls. Reproduction-related clinical outcomes of patients in the three groups were compared.
  
  
  RESULTS
  The embryo implantation rate of patients in letrozole group (30.4 %) was significantly higher than the HRT group (22.8 %, P < 0.05). The clinical pregnancy rate of patients in the letrozole group (53.2 %) was significantly higher than the HRT group (44.4 %, P < 0.05), while no significant difference was observed between the letrozole and natural cycle groups (51.3 %, P > 0.05). Estradiol levels on the day of human chorionic gonadotropin administration in the letrozole group were significantly lower than those in the natural cycle group (280.32 ± 125.39 pg/ml and 351.06 ± 123.03 pg/ml, respectively; P < 0.05). The live birth rate of patients in letrozole group (44.6 %) was significantly higher than the HRT group (32.5 %, P < 0.05), while abortion rate (12.0 %) was significantly lower than the HRT group (21.0 %, P < 0.05). There were no significant differences in number of mature follicles, endometrial thickness, duration of follicle growth between the letrozole and the natural cycle groups, and there were no significant differences in twin birth rate and ectopic pregnancy rate among the three groups (all P values >0.05).
  
  
  CONCLUSIONS
  Ovulation induction with letrozole during endometrial preparation for FET has a higher rate of pregnancy success and a lower abortion rate than HRT. Letrozole treatment exhibits clinical progression and outcomes similar to those patients undergoing a natural cycle or normal ovulation cycle. Therefore, letrozole treatment may be an effective option in endometrial preparation for FET in patients with ovulation disorders or irregular menstruation.
authors.forename: Song-jun
authors.initials: SJ
authors.lastname: Li
authors.forename: Yong-jing
authors.initials: YJ
authors.lastname: Zhang
authors.forename: Xiao-shan
authors.initials: XS
authors.lastname: Chai
authors.forename: Mei-fang
authors.initials: MF
authors.lastname: Nie
authors.forename: Yu-yan
authors.initials: YY
authors.lastname: Zhou
authors.forename: Jian-lin
authors.initials: JL
authors.lastname: Chen
authors.forename: Guang-shi
authors.initials: GS
authors.lastname: Tao
mesh_terms: D000022:Abortion, Spontaneous / Q000453:epidemiology; D000328:Adult; D047072:Aromatase Inhibitors / Q000494:pharmacology*; D001723:Birth Rate; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D015925:Cryopreservation; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000379:methods*; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D000077289:Letrozole; D009570:Nitriles / Q000494:pharmacology*; D006080:Ovarian Follicle / Q000187:drug effects; D010062:Ovulation Induction / Q000379:methods*; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D011271:Pregnancy, Ectopic / Q000453:epidemiology; D014230:Triazoles / Q000494:pharmacology*
chemical_list: D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D000077289:Letrozole