title: Clomiphene citrate vs. letrozole for cryopreserved-thawed embryo transfer: a randomized, controlled trial.
abstract: OBJECTIVE
  To assess the endometrial thickness, hormonal status and pregnancy rates with clomiphene citrate (CC) vs. letrozole in frozen-thawed embryo transfer protocols.
  
  
  METHODS
  Nineteen patients who had previously undergone in vitro fertilization (IVF) with embryo cryopreservation were prospectively and randomly enrolled in a randomized, controlled trial. Nine patients were treated with CC, 100 mg per day, from day 3 to day 7 of the cycle, and 10 patients were treated with letrozole, 2.5 mg per day, on the same cycle days. beta-Human chorionic gonadotropin (beta-hCG) was administrated when the leading follicular size was > or = 18 mm. Endometrial thickness was measured on cycle day 8, beta-hCG day, transfer day and 7 days after embryo transfer. Estradiol levels were determined on the day of beta-hCG administration.
  
  
  RESULTS
  Patients' ages and number of previous unsuccessful IVF cycles were similar between the 2 groups. Endometrial thickness was significantly higher in the letrozole group as compared to the CC group on the day of beta-hCG administration (9.1 +/- 3.6 vs. 6.9 +/- 1.2 mm, p<0.05), on the day of embryo transfer (10 +/- 1.7 vs. 7.6 +/- 1.4 mm, p<0.05) and 7 days after embryo transfer (12.2 +/- 0.4 vs. 9.0 +/- 3.0 mm, p<0.05). Estradiol levels in the letrozole group were significantly lower than in the CC group on the beta-hCG day (231 +/- 132 vs. 515 +/- 363 pg/L, p<0.05). Pregnancy was not achieved in either group.
  
  
  CONCLUSIONS
  Endometrial thickness is improved by letrozole as compared to CC in frozen-thawed embryo transfer cycles. Further investigation is needed to assess pregnancy and implantation rates.
authors.affiliation: Sarah Racine IVF Unit, Tel-Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
authors.forename: Israel
authors.initials: I
authors.lastname: Wagman
authors.forename: Ishai
authors.initials: I
authors.lastname: Levin
authors.forename: Rita
authors.initials: R
authors.lastname: Kapustiansky
authors.forename: Alon
authors.initials: A
authors.lastname: Shrim
authors.forename: Ami
authors.initials: A
authors.lastname: Amit
authors.forename: Benny
authors.initials: B
authors.lastname: Almog
authors.forename: Fuad
authors.initials: F
authors.lastname: Azem
mesh_terms: D000328:Adult; D002996:Clomiphene / Q000627:therapeutic use*; D015925:Cryopreservation; D004624:Embryo Transfer; D004717:Endometrium / Q000000981:diagnostic imaging; D004958:Estradiol / Q000097:blood; D005260:Female; D005300:Fertility Agents, Female / Q000627:therapeutic use*; D006801:Humans; D000077289:Letrozole; D009570:Nitriles / Q000627:therapeutic use*; D010062:Ovulation Induction / Q000379:methods*; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D014230:Triazoles / Q000627:therapeutic use*; D014463:Ultrasonography
chemical_list: D005300:Fertility Agents, Female; D009570:Nitriles; D014230:Triazoles; D002996:Clomiphene; D004958:Estradiol; D000077289:Letrozole