title: A comparison of letrozole to gonadotropins for ovulation induction, in subjects who failed to conceive with clomiphene citrate.
abstract: OBJECTIVE
  To compare pregnancy rates (PR) for letrozole and gonadotropins in individuals who failed to conceive with clomiphene citrate (CC).
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  University reproductive center.
  
  
  METHODS
  Individuals treated with letrozole or gonadotropins who failed to conceive with CC.
  
  
  METHODS
  Controlled ovarian hyperstimulation (COH), transvaginal ultrasound, ovulation induction, IUI.
  
  
  METHODS
  Pregnancy rates per cycle.
  
  
  RESULTS
  Among patients who failed to conceive with at least three cycles of CC, gonadotropins had a higher PR per cycle than letrozole. Among individuals who failed to conceive with less than three cycles of CC and whose medications were changed because of thin uterine lining or intolerable side effects, average PR per cycle for letrozole and gonadotropin treatments were equivalent. All patients conceived within three stimulation cycles with either gonadotropins or letrozole.
  
  
  CONCLUSIONS
  In patients who failed to conceive with CC, gonadotropins have higher PR for ovulation induction than letrozole. However, PR were high enough with letrozole to justify its use in this population of patients. Letrozole and gonadotropins should not be used for more than three cycles without a conception.
authors.affiliation: Division of Reproductive Endocrinology and Infertility, Department of Obstetrics and Gynecology, Stanford University, Stanford, CA 94305-5317, USA.
authors.forename: Rudolfo B
authors.initials: RB
authors.lastname: Quintero
authors.forename: Renata
authors.initials: R
authors.lastname: Urban
authors.forename: Ruth B
authors.initials: RB
authors.lastname: Lathi
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Westphal
authors.forename: Michael H
authors.initials: MH
authors.lastname: Dahan
mesh_terms: D000328:Adult; D047072:Aromatase Inhibitors / Q000627:therapeutic use*; D002996:Clomiphene / Q000627:therapeutic use; D015331:Cohort Studies; D005260:Female; D005640:Follicle Stimulating Hormone / Q000627:therapeutic use*; D006801:Humans; D000077289:Letrozole; D009570:Nitriles / Q000627:therapeutic use*; D010062:Ovulation Induction / Q000379:methods*; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D012189:Retrospective Studies; D014230:Triazoles / Q000627:therapeutic use*
chemical_list: D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D002996:Clomiphene; D000077289:Letrozole; D005640:Follicle Stimulating Hormone