The composition of menstrual fluid, its applications, and recent advances to understand the endometrial environment: a narrative review

Research into menstrual fluid (MF), also referred to as menstrual blood or effluent in the literature, and its potential as a diagnostic tool has been largely overlooked. The current understanding of the endometrium has been principally derived from invasive techniques, such as endometrial biopsies, yet endometrial tissue is cyclically shed in MF. Menstrual fluid has a composition that distinctly reflects the endometrial environment and provides an easily accessible source of endometrial constituents that can be collected relatively noninvasively using a menstrual cup. Menstrual fluid offers a renewable and inexpensive option that has the potential to replace more invasive and uncomfortable methods of collecting endometrial samples. Menstrual health can provide invaluable insight into the endometrial environment and the development of endometrial disorders. Menstrual fluid has been recently utilized to research the pathogenesis of endometriosis, chronic endometritis, and unexplained infertility; however, some logistical challenges in the recruitment of participants, collection, and processing of MF samples require optimization. This review detailed what we currently know about the composition of MF and the recent advances in MF research, as well as future directions. Menstrual fluid provides a unique window into the endometrium, and further research could help uncover the pathogenesis of endometrial disorders and have exciting prospects as a diagnostic tool.