Korean J Reprod Med.  2010 Mar;37(1):73-81.

The Efficacy of Letrozole in Women with a Poor Endometrial Response to Clomiphene Citrate

  • 1Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea. blasto@snubh.org
  • 2Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea.


To examine the efficacy of letrozole in infertile women showing a poor endometrial development at previous ovulation induction cycle by using clomiphene citrate.
Eighteen infertile women were selected who showed a poor endometrial development (endometrial thickness< or =6.5 mm) after clomiphene treatment (50~100 mg) as ovulation induction for timed coitus. The mean age of the patients was 30.7+/-2.8 years old and the mean duration of infertility was 33.1+/-26.6 months. The infertility factors were identified as corrected endometriosis (n=1), polycystic ovary syndrome (n=5) and unexplained (n=12). Letrozole was given orally in a dose of 2.5 mg for 5 days starting 3~5 of menstrual cycle.
The number of follicles was significantly lower in the letrozole cycle when compared with previous clomiphene cycle (1.1+/-0.3 vs. 2.2+/-1.5, p=0.011). The endometrial thickness (mm) at the time of triggering or LH surge was significantly greater in the letrozole cycle (8.4+/-1.7 vs. 5.8+/-0.5, p<0.001). The endometrial pattern 'type C' was significantly higher in the letrozole cycle (94.4% vs. 50%, p=0.036). The pregnancy was achieved in 11.1% of the letrozole cycle.
Use of letrozole was associated with more thick and improved endometrium than previous clomiphene cycles in which thin endometrium was identified. Use of letrozole appears to be an effective strategy for second-line treatment in women with inadequate endometrial response to clomiphene.


Letrozole; Clomiphene; Ovulation induction; Endometrium
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