Improving the Quality of the Reporting of Systematic Reviews and Meta-analyses

We read with great interest an article entitled “Prevalence of Birth Defects in Iran: A Systematic Review and Meta-Analysis”, published in July2017 in your valuable Journal.1 Systematic reviews (SRs) and meta-analytic (MA) studies can be very effective and valuable for health-care workers and policy-makers, since they provide updated and reliable scientific evidences. Authors should be commended for their efforts; however we have the following observations. Because of methodological differences among studies (in terms, for example, of study design, sample size, different criteria or tests, study province/region, etc.) and different kinds of biases such as selection bias, attrition bias, detection bias, and performance bias, the authors could have stratified their meta-analysis based on the quality of studies.