A comparative study of efficacy of letrozole and clomiphene citrate for ovulation induction


  • Shaveta Jain Department of Obstetrics and Gynecology, Pt. B. D. Sharma, PGIMS, University of Health Sciences, Rohtak, Haryana, India
  • Pushpa Dahiya Department of Obstetrics and Gynecology, Pt. B. D. Sharma, PGIMS, University of Health Sciences, Rohtak, Haryana, India
  • Jyoti Yadav Department of Obstetrics and Gynecology, Pt. B. D. Sharma, PGIMS, University of Health Sciences, Rohtak, Haryana, India
  • Nitin Jain Department of Radiology, Advanta Super Specialty Hospital and Trauma Centre, Rohtak, Haryana, India




Aromatase inhibitor, Clomiphene, Infertility, Letrozole, Ovulation


Background: This study was conducted to evaluate the efficacy of letrozole as an ovulation inducing agent and to compare it with clomiphene citrate (CC) in infertile women.

Methods: This study includes 100 women referred to gynecology OPD of Pt. B.D Sharma, PGIMS, Rohtak with   infertility due to dysovulation. The patients were divided in two groups each comprised of 50 patients, Alternate women were enrolled in study group (Letrozole). Ultrasonic follicular monitoring was done on day 10, 12, 14, 16 of menstrual cycle to measure the number, size of mature follicles. Endometrial thickness and trilaminar pattern of endometrium was compared in between the groups. Inj. Gonadotrophin (hCG) was given as a trigger intramuscularly when follicle size was between 18 to 21mm. After 36 hours of hCG administration ovulation was confirmed on ultrasound.

Results: Mean age, parity, and the duration of infertility were similar in both groups. Ovulation rate was 81.6% in letrozole group and was higher than control group(p<.01). The average number of follicles in the control group was 1.90±0.77and 1.17±0.47 in the study group(p<.001). Endometrial thickness in the study group was 7.55±1.12mm and in the control group it was 6.06±0.87(p<.01). Pregnancy rate in study group was 48 % and control group 16%(p<.05).

Conclusions: Aromatase inhibitors (Letrozole) is a new group of drugs to join the arsenal of infertility treatments. The result of this preliminary study suggests that letrozole is associated with higher ovulation rate, higher endometrial thickness and trilaminar pattern thus resulting in higher pregnancy rate. Clomiphene citrate may be replaced by letrozole as primary treatment for ovulation induction in infertile patients.


Burney RO Sclurst DJ, Mayao MW. Infertility. In: Berek JS, eds. Berek and Novak’s Gynecology. 14th ed. New Delhi: Woltens Kluvenhealth; 2007:1185-1276.

Speroff L, Fritz MA, editors. Female infertility. In: Clinical gynaecologic endocrinology infertility. 7th ed. Philadelphia: Lippincott William and Wilkins; 2007: 1013-1068.

Carcio AH, ed. Causes of infertility. In: Management of infertile couple. Lippincott: Raven Publishers. 1999: 25-48.

Blumenfeld Z, Yoffe N, Bronshtein M. Transvaginal sonography in infertility and assisted reproduction a review. Obstet Gynaecol Survey .1990;36-49.

Holzer H, Casper R, Tulandi T. A new era in ovulation induction. Fertil Steril. 2006;85:277-84.

Bayar U, Tranriverdi HA, Barut A, Ayoglu F, Ozcan O, Kaya E. Letrozole vs clomiphene citrate in patients with ovulatory infertility. Fertil Steril. 2006;85:1045-8.

Atay VC, Muhcu M, Cam M, Karateke A. Comparison of Letrozole and clomiphene cirate in women with polycystic ovaries undergoing ovarian stimulation. J Int Med Res. 2006;34:73-6.

Mitwally MFM, Casper RF. Use of an aromatase inhibitor for induction of ovulation in patients with an inadequate response to clomiphene citrate. Fertil Steril. 2001;75:305-9

Sioufi A, Gauducheau N, Pineau V, Marfil F, Jaouen A, Cardot JM, et al. Absolute bioavailability of letrozole in healthy postmenopausal women. Biopharmac Drug Disposition. 1997;18(9):779-89.

Kerin JF, Liu JH, Phillipou G, Yen SSS. Evidence for a hypothalamic site of action of clomiphene citrate in women. J Clin Endocrinol Metab. 1985;61:265-8.

Fisher SA, Rold RL, Vugt DA, Casper RF. A randomized double-blind comparison of effects of clomiphene citrate and the aromatase inhibitor letrozole on ovulatory function in normal women. Fertil Steril. 2002;78:280-5.

Sammour A, Biljan MM, Tan SL, Tulandi T. Prospective randomized trial comparing the effects of letrozole (LE) and clomiphene citrate (CC) on follicular development, endometrial thickness and pregnancy rate in patients undergoing super-ovulation prior to intrauterine insemination (IUI). Fertil Steril. 2001;76:110-7.

Al-Fozan H, Al-Khadouri M, Tan SL, Tulandi T. A randomized trial of letrozole versus clomiphene citrate in women undergoing superovulation. Fertil Steril. 2004;82:1561-3.

Hammond M, Halme J, Talbert L. Factors affecting the pregnancy rate in clomiphene citrate induction of ovulation. Obstet Gynaecol. 1983;62:196-202.

Gonen Y, Casper RF. Sonographic determination of an adverse effect of clomiphene citrate on endometrial growth. Hum Reprod. 1990;5:670-4.

Begum MR, Quadir E, Begum A, Begum RH, Begum M. Role of aromatase inhibitor in ovulation induction in patients with poor response to clomiphene citrate. J Obstet Gynaecol Res. 2006;32:502-6.






Original Research Articles