The importance of mediation in reproductive health studies.

A mediator is a factor that occurs after the exposure of interest, precedes the outcome of interest (i.e. between the exposure and the outcome) and is associated with both the exposure and the outcome of interest (i.e. is on the pathway between exposure and outcome). Mediation analyses can be valuable in many reproductive health contexts, as mediation analysis can help researchers to better identify, quantify and understand the underlying pathways of the association they are studying. The purpose of this commentary is to introduce the concept of mediation and provide examples that solidify understanding of mediation for valid discovery and interpretation in the field of reproductive medicine.