A call for clarity in infant breast and bottle-feeding definitions for research.

Unclear and inconsistent infant-feeding definitions have plagued much of breastfeeding research. To determine accurate health outcomes associated with infant feeding, it is imperative that different types of feedings be explicitly described. Definitions must be based on content, not mode of milk delivery. Five new definitions for infant feeding are provided. These definitions are operationally useful for breastfeeding researchers, allowing for the inclusion of almost every infant into an appropriate sample group.