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What is the optimal follicular size before triggering ovulation in intrauterine insemination cycles with clomiphene citrate or letrozole? An analysis of 988 cycles. Fertil Steril 2012 May;97(5):1089-94.e1-3 PMID: 22459633

Pubmed ID



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.

DESIGN: A retrospective study.

SETTING: University hospital-based reproductive center.

PATIENT(S): 1,075 women undergoing intrauterine insemination cycles with CC or letrozole.

INTERVENTION(S): 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.

MAIN OUTCOME MEASURE(S): Leading follicle diameter and intrauterine insemination outcome.

RESULT(S): 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.

CONCLUSION(S): 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.

Author List

Palatnik A, Strawn E, Szabo A, Robb P


Anna Palatnik MD Assistant Professor in the Obstetrics and Gynecology department at Medical College of Wisconsin
Aniko Szabo PhD Associate Professor in the Institute for Health and Equity department at Medical College of Wisconsin


2-s2.0-84860347503   16 Citations

MESH terms used to index this publication - Major topics in bold

Chi-Square Distribution
Chorionic Gonadotropin
Drug Administration Schedule
Drug Therapy, Combination
Fertility Agents, Female
Insemination, Artificial
Logistic Models
Multivariate Analysis
Ovarian Follicle
Ovulation Induction
Pregnancy Rate
Retrospective Studies
Time Factors
Treatment Outcome
jenkins-FCD Prod-299 9ef562391eceb2b8f95265c767fbba1ce5a52fd6