First-line ovulation induction for polycystic ovary syndrome: an individual participant data meta-analysis

Rui Wang* (Corresponding Author), Wentao Li, Esmée M. Bordewijk, Richard S. Legro, Heping Zhang, Xiaoke Wu, Jingshu Gao, Laure Morin-Papunen, Roy Homburg, Tamar E. König, Etelka Moll, Sujata Kar, Wei Huang, Neil P. Johnson, Saad A. Amer, Walter Vegetti, Stefano Palomba, Angela Falbo, Ülkü Özmen, Hakan NazikChristopher D. Williams, Grasso Federica, Jonathan Lord, Yilmaz Sahin, Siladitya Bhattacharya, Robert J. Norman, Madelon van Wely, Ben Willem Mol, Reproductive Medicine Network+, International Ovulation Induction IPDMA Collaboration

*Corresponding author for this work

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Polycystic ovary syndrome (PCOS) is the most frequent cause of anovulatory infertility. In women with PCOS, effective ovulation induction serves as an important first-line treatment for anovulatory infertility. Individual participant data (IPD) meta-analysis is considered as the gold standard for evidence synthesis which provides accurate assessments of outcomes from primary randomised controlled trials (RCTs) and allows additional analyses for time-to-event outcomes. It also facilitates treatment–covariate interaction analyses and therefore offers an opportunity for personalised medicine.

We aimed to evaluate the effectiveness of different ovulation induction agents, in particular letrozole alone and clomiphene citrate (CC) plus metformin, as compared to CC alone, as the first-line choice for ovulation induction in women with PCOS and infertility, and to explore interactions between treatment and participant-level baseline characteristics.

We searched electronic databases including MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials up to 20 December 2018. We included RCTs comparing the following interventions with each other or placebo/no treatment in women with PCOS and infertility: CC, metformin, CC plus metformin, letrozole, gonadotrophin and tamoxifen. We excluded studies on treatment-resistant women. The primary outcome was live birth. We contacted the investigators of eligible RCTs to share the IPD and performed IPD meta-analyses. We assessed the risk of bias by using the Cochrane risk of bias tool for RCTs.

IPD of 20 RCTs including 3962 women with PCOS were obtained. Six RCTs compared letrozole and CC in 1284 women. Compared with CC, letrozole improved live birth rates (3 RCTs, 1043 women, risk ratio [RR] 1.43, 95% confidence interval [CI] 1.17–1.75, moderate-certainty evidence) and clinical pregnancy rates (6 RCTs, 1284 women, RR 1.45, 95% CI 1.23–1.70, moderate-certainty evidence) and reduced time-to-pregnancy (6 RCTs, 1235 women, hazard ratio [HR] 1.72, 95% CI 1.38–2.15, moderate-certainty evidence). Meta-analyses of effect modifications showed a positive interaction between baseline serum total testosterone levels and treatment effects on live birth (interaction RR 1.29, 95% CI 1.01–1.65). Eight RCTs compared CC plus metformin to CC alone in 1039 women. Compared with CC alone, CC plus metformin might improve clinical pregnancy rates (8 RCTs, 1039 women, RR 1.18, 95% CI 1.00–1.39, low-certainty evidence) and might reduce time-to-pregnancy (7 RCTs, 898 women, HR 1.25, 95% CI 1.00–1.57, low-certainty evidence), but there was insufficient evidence of a difference on live birth rates (5 RCTs, 907 women, RR 1.08, 95% CI 0.87–1.35, low-certainty evidence). Meta-analyses of effect modifications showed a positive interaction between baseline insulin levels and treatment effects on live birth in the comparison between CC plus metformin and CC (interaction RR 1.03, 95% CI 1.01–1.06).

In women with PCOS, letrozole improves live birth and clinical pregnancy rates and reduces time-to-pregnancy compared to CC and therefore can be recommended as the preferred first-line treatment for women with PCOS and infertility. CC plus metformin may increase clinical pregnancy and may reduce time-to-pregnancy compared to CC alone, while there is insufficient evidence of a difference on live birth. Treatment effects of letrozole are influenced by baseline serum levels of total testosterone, while those of CC plus metformin are affected by baseline serum levels of insulin. These interactions between treatments and biomarkers on hyperandrogenaemia and insulin resistance provide further insights into a personalised approach for the management of anovulatory infertility related to PCOS.
Original languageEnglish
Pages (from-to)717-732
Number of pages16
JournalHuman Reproduction Update
Issue number6
Early online date23 Oct 2019
Publication statusPublished - 5 Nov 2019

Bibliographical note

We would like to thank Mr M. Draper from Barr Smith Library, University of Adelaide, for his assistance in developing the search strategies and Dr M. H. Zafarmand from University of Amsterdam for assisting with the translation. We would like to acknowledge all the investigators and participants of the primary trials. The investigators of individual trials are listed in Supplementary Table SIV. We would like to acknowledge the assistance of NICHD, the Reproductive Medicine Network (RMN) and the Protocol Subcommittee, in making the database for PPCOS I and II available. +The authors of the Reproductive Medicine Network are R.S.L., R.G. Brzyski, M.P. Diamond, C. Coutifaris, W.D. Schlaff, P. Casson, G.M. Christman, H. Huang, Q. Yan, R. Alvero, D.J. Haisenleder, K.T. Barnhart, G.W. Bates, R. Usadi, S. Lucidi, V. Baker, J.C. Trussell, S.A. Krawetz, P. Snyder, D. Ohl, N. Santoro, H.X. Barnhart, B.R. Carr, S.A. Carson, M.P. Steinkampf, P.G. McGovern, N.A. Cataldo, G.G. Gosman, J.E. Nestler, L.C. Giudice, P.C. Leppert, E.R. Myers, E. Eisenberg and H. Zhang. The details of their affiliations and NIH Grants are listed in Supplementary Table SV.

An Australian government research training programme scholarship (to R.W.); Australian National Health and Medical Research Council-funded Centre for Research Excellence in Polycystic Ovary Syndrome (APP1078444).

The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.


  • polycystic ovary syndrome
  • infertility
  • anovulation
  • ovulation induction
  • letrozole
  • clomiphene
  • metformin
  • individual participant data
  • meta-analysis


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