title: What is the optimal follicular size before triggering ovulation in intrauterine insemination cycles with clomiphene citrate or letrozole? An analysis of 988 cycles.
abstract: OBJECTIVE
  To determine the optimal size of the leading follicle before human chorionic gonadotropin (hCG) administration in cycles with clomiphene citrate (CC) and letrozole, and to examine any differences in the optimal leading follicle size between cycles with CC and letrozole.
  
  
  METHODS
  A retrospective study.
  
  
  METHODS
  University hospital-based reproductive center.
  
  
  METHODS
  1,075 women undergoing intrauterine insemination cycles with CC or letrozole.
  
  
  METHODS
  Leading follicle diameters and endometrial thickness were recorded 24 hours before hCG administration, together with other cycles parameters, and were compared between pregnant and nonpregnant patients.
  
  
  METHODS
  Leading follicle diameter and intrauterine insemination outcome.
  
  
  RESULTS
  Eight percent of patients (n = 87) were excluded because their leading follicle was less than 18 mm by days 11 to 13. Pregnancy was recorded as clinical pregnancy with fetal heart activity seen at 6- to 7-week transvaginal ultrasound. For both CC and letrozole, higher pregnancy rates were achieved when the leading follicles were in the 23 to 28 mm range. The optimal size of the leading follicle was not statistically significantly different between cycles using CC or letrozole. However, for each endometrial thickness, the optimal follicular size of the leading follicle was different. Each additional millimeter of endometrial thickness increased the optimal follicular size by 0.5 mm. Thicker endometrial lining led to a higher probability of pregnancy.
  
  
  CONCLUSIONS
  The optimal size of the leading follicle in ovulation induction with CC and letrozole is similar for both drugs and is closely related to the endometrial thickness.
authors.affiliation: Department of Obstetrics and Gynecology, Froedtert Hospital, Medical College of Wisconsin Affiliated Hospitals, Milwaukee, Wisconsin 53226, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Palatnik
authors.forename: Estil
authors.initials: E
authors.lastname: Strawn
authors.forename: Aniko
authors.initials: A
authors.lastname: Szabo
authors.forename: Paul
authors.initials: P
authors.lastname: Robb
mesh_terms: D000328:Adult; D016009:Chi-Square Distribution; D006063:Chorionic Gonadotropin / Q000008:administration & dosage*; D002996:Clomiphene / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D004359:Drug Therapy, Combination; D004717:Endometrium / Q000000981:diagnostic imaging; D005260:Female; D005300:Fertility Agents, Female / Q000008:administration & dosage*; D006801:Humans; D007246:Infertility / Q000503:physiopathology / Q000628:therapy*; D007315:Insemination, Artificial; D000077289:Letrozole; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D009570:Nitriles / Q000008:administration & dosage*; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000187:drug effects*; D010060:Ovulation / Q000187:drug effects*; D010062:Ovulation Induction / Q000379:methods*; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D014230:Triazoles / Q000008:administration & dosage*; D014463:Ultrasonography; D014922:Wisconsin
chemical_list: D006063:Chorionic Gonadotropin; D005300:Fertility Agents, Female; D009570:Nitriles; D014230:Triazoles; D002996:Clomiphene; D000077289:Letrozole