This systematic review aims to identify and evaluate mammalian reproductive studies assessing the potential effects associated with microplastics in the context of hazard and risk assessment (including dose-response). During this review process, emphasis will be placed on the refinement of critical appraisal approaches to evaluate the internal and construct validity of each relevant study based on known methodological attributes important to microplastics and the outcomes of interest. Additionally, criteria and best practices to be considered for future reproductive toxicity studies of microplastics will be discussed.