Meta-analysis: drawing conclusions when study results vary.

Low-dose aspirin has been suggested to positively impact a number of clinical outcomes associated with oxidative stress; however, results of clinical trials surrounding its effect on a woman's ability to achieve and sustain pregnancy have been inconclusive. A meta-analysis is an advantageous tool in this situation. Meta-analyses allow researchers to formally and systematically pool together all relevant research in order to clarify findings and form conclusions based on all currently available information. The purpose of this chapter is to describe how to perform a meta-analysis, clarify the impact of model selection, and provide examples of implementation.