Best protocol for controlled ovarian hyperstimulation in assisted reproductive technologies: fact or opinion?

From the early ages of assisted reproductive technologies (ARTs), different protocols have been developed with different gonadotropin preparations at different dosages with or without gonadotropin releasing hormone agonist or antagonist cotreatment. Various adjuvants have also been incorporated in controlled ovarian hyperstimulation (COH) protocols in an attempt to increase the efficacy and safety. The "best" protocol for COH should minimize stimulation burden while maintain the highest healthy, singleton, term live birth rates. Understandably, the one that meets all these expectations may not exist and COH should be individualized. Currently, there are worldwide differences in COH protocols and gonadotropin dose algorithms used depending on the country, demographics, funding stream, and existing guidelines/legislations. In 2014, despite efforts to individualize COH, currently, many of the protocols employ lack of high-quality evidence-based data. The aim of this review is to overview the efficacy and safety of available COH protocols, in normal responders, poor responders, and hyperresponders from evidence-based medicine perspective.