Meta-analysis of letrozole versus clomiphene citrate in polycystic ovary syndrome

Reprod Biomed Online. 2011 Jul;23(1):91-6. doi: 10.1016/j.rbmo.2011.03.024. Epub 2011 Apr 3.


The aim of this study was to systematically compare the clinical efficacy and safety of letrozole with clomiphene citrate for ovulation induction in women with polycystic ovary syndrome (PCOS). The Cochrane Central Register of Controlled Trials, PubMed, EMbase, CBMdisc and CNKI were searched for eligible randomized controlled trials (RCT) comparing letrozole with clomiphene citrate in PCOS patients. Two reviewers independently extracted information and evaluated methodological quality according to the Cochrane Handbook 5.0. Meta-analysis was performed with the fixed-effects model or random-effects model according to the heterogeneity. Six eligible RCT involving 841 patients were included. Letrozole was associated with a number of lower mature follicles per cycle (standardized mean difference (SMD) -1.41; 95% confidence intervales (CI) -1.54 to -1.28; P<0.00001) compared with clomiphene citrate. There were no significant differences in pregnancy rate (relative risk (RR) 0.97; 95% CI 0.79 to 1.18), abortion rate (RR 1.38; 95% CI 0.48 to -3.96) and multiple pregnancy rate (RR 0.34; 95% CI 0.07 to -1.72) between the two groups. The evidence from ovulation rates was not enough to support either letrozole or clomiphene citrate. In conclusion, letrozole is as effective as clomiphene citrate for ovulation induction in patients with PCOS.

Publication types

  • Meta-Analysis
  • Review

MeSH terms

  • Clomiphene / therapeutic use*
  • Female
  • Fertility Agents, Female / therapeutic use*
  • Humans
  • Letrozole
  • Nitriles / therapeutic use*
  • Ovulation Induction / methods*
  • Polycystic Ovary Syndrome / drug therapy*
  • Pregnancy
  • Pregnancy Rate
  • Randomized Controlled Trials as Topic
  • Treatment Outcome
  • Triazoles / therapeutic use*


  • Fertility Agents, Female
  • Nitriles
  • Triazoles
  • Clomiphene
  • Letrozole