To update the state of evidence on the efficacy of metformin, used either alone or in combination with clomiphene citrate in women with polycystic ovary syndrome, by examining three outcomes: ovulation, pregnancy, and live birth. Sources of heterogeneity among the published randomized controlled trials are systematically assessed.
An electronic literature search was performed using MEDLINE, EMBASE, SCOPUS, CENTRAL, Cochrane, and U.S. Food and Drug Administration databases, restricted to studies conducted on humans and published in English.
Of the 406 potentially relevant articles identified, 17 met criteria for inclusion in the meta-analysis, rendering a total sample of 1,639 women. Study quality was examined in terms of randomization scheme, masking process, adequacy of allocation concealment, statistical power, and loss to follow-up; publication bias was also assessed. Meta-analytic procedures were used to compare metformin with placebo, and metformin plus clomiphene with clomiphene alone, for all study outcomes. Exploratory analyses were conducted to assess differences in treatment effects between clomiphene-resistant and nonresistant patients, obese and nonobese patients, and trials with long and short durations of follow-up.
Metformin improved the odds of ovulation in women with polycystic ovary syndrome when compared with placebo (odds ratio [OR] 2.94; 95% confidence interval [CI] 1.43–6.02; number-needed-to-treat 4.0) and appears more effective for non–clomiphene-resistant women. Metformin and clomiphene increased the likelihood of ovulation (OR 4.39; 95% CI 1.94–9.96; number-needed-to-treat 3.7) and pregnancy (OR 2.67; 95% CI 1.45–4.94; number-needed-to-treat 4.6) when compared with clomiphene alone, especially in clomiphene-resistant and obese women with polycystic ovary syndrome. These treatment effects were greater for trials with shorter follow-up.
Using all available evidence, this meta-analysis suggests that metformin increases the likelihood of ovulation and, in combination with clomiphene, increases the odds of both ovulation and pregnancy in women with polycystic ovary syndrome.
Metformin increases the likelihood of ovulation in women with polycystic ovary syndrome and, in combination with clomiphene, increases the odds of both ovulation and pregnancy.
From the 1Department of Population, Family and Reproductive Health, Johns Hopkins Bloomberg School of Public Health; 2Department of Obstetrics and Gynecology, the Kelly Gynecologic Oncology Service, Johns Hopkins School of Medicine; and 3Department of General Preventive Medicine, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
The authors thank Dr. Kelly Stein for her contribution in reviewing abstracts and selected papers.
Presented at the 2007 American College of Obstetricians and Gynecologists Armed Forces District Annual Meeting, October 28–31, 2007, Louisville, Kentucky.
Corresponding author: Andreea A. Creanga, Johns Hopkins Bloomberg School of Public Health, Department of Population, Family and Reproductive Health, 615 N. Wolfe Street, Room W4513, Baltimore, MD 21201; e-mail: firstname.lastname@example.org.
Financial Disclosure The authors have no potential conflicts of interest to disclose.