Aromatase inhibitors for PCOS: a systematic review and meta-analysis

Hum Reprod Update. 2012 May-Jun;18(3):301-12. doi: 10.1093/humupd/dms003. Epub 2012 Mar 19.


Background: The effectiveness of aromatase inhibitors (AIs) in the treatment of anovulatory polycystic ovary syndrome (PCOS) remains unclear. The objective was to determine whether AIs are effective in improving fertility outcomes in women with PCOS.

Methods: Databases were searched until July 2011. Inclusion criteria were women with PCOS, who are infertile, receiving any type, dose and frequency of AI compared with placebo, no other treatment or other infertility treatment. Outcomes were rates of: ovulation, pregnancy, live birth, multiple pregnancies, miscarriage and adverse events, as well as quality of life and cost effectiveness. Data were extracted and risk of bias was assessed. A random-effects model was used for the meta-analyses, using odds ratios (ORs) and rate ratios (RRs).

Results: The search returned 4981 articles, 78 articles addressed AIs and 13 randomized controlled trials (RCTs) met the inclusion criteria. No RCTs compared AIs versus placebo or no treatment, in therapy naïve women with PCOS. Meta-analyses of six RCTs comparing letrozole with clompihene citrate (CC) demonstrated that letrozole improved the ovulation rate per patient [OR 2.90 (95% confidence interval (CI) 1.72, 4.88), I(2) = 0%, P < 0.0001]; however, there was no statistical difference for the ovulation rate per cycle or the pregnancy, live birth, multiple pregnancy or miscarriage rates. Letrozole also did not improve pregnancy or live birth rates compared with placebo or with CC plus metoformin in women with CC-resistant PCOS. Results of comparisons of letrozole and anastrozole in women with CC-resistant PCOS were conflicting in terms of ovulation and pregnancy rates.

Conclusions: In the absence of supportive high-quality evidence, AIs should not be recommended as the first-line pharmacological therapy for infertility in women with PCOS, and further research is needed.

Publication types

  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Review
  • Systematic Review

MeSH terms

  • Anastrozole
  • Aromatase Inhibitors / therapeutic use*
  • Female
  • Humans
  • Infertility, Female / drug therapy*
  • Letrozole
  • Live Birth
  • Nitriles / therapeutic use
  • Ovulation / drug effects
  • Polycystic Ovary Syndrome / drug therapy*
  • Pregnancy
  • Pregnancy Rate
  • Pregnancy, Multiple
  • Randomized Controlled Trials as Topic
  • Triazoles / therapeutic use


  • Aromatase Inhibitors
  • Nitriles
  • Triazoles
  • Anastrozole
  • Letrozole