Uterine bleeding: how understanding endometrial physiology underpins menstrual health

Abnormal uterine bleeding affects many individuals who menstruate and can have a detrimental impact on physical and mental health. This Review discusses endometrial physiology and the causes underlying abnormal uterine bleeding (including heavy menstrual bleeding). Menstruation is a physiological process that is typically uncomplicated. However, up to one third of women globally will be affected by abnormal uterine bleeding (AUB) at some point in their reproductive years. Menstruation (that is, endometrial shedding) is a fine balance between proliferation, decidualization, inflammation, hypoxia, apoptosis, haemostasis, vasoconstriction and, finally, repair and regeneration. An imbalance in any one of these processes can lead to the abnormal endometrial phenotype of AUB. Poor menstrual health has a negative impact on a person's physical, mental, social, emotional and financial well-being. On a global scale, iron deficiency and iron deficiency anaemia are closely linked with AUB, and are often under-reported and under-recognized. The International Federation of Gynecology and Obstetrics have produced standardized terminology and a classification system for the causes of AUB. This standardization will facilitate future research endeavours, diagnosis and clinical management. In a field where no new medications have been developed for over 20 years, emerging technologies are paving the way for a deeper understanding of the biology of the endometrium in health and disease, as well as opening up novel diagnostic and management avenues.

Automated summary

Abnormal uterine bleeding can adversely affect the physical and mental health of individuals who menstruate. This Review explores the causes and physiology of abnormal uterine bleeding. Menstruation is a normal physiological process, but one third of women globally experience abnormal uterine bleeding during their reproductive years. Imbalances in various stages of endometrial shedding can result in the abnormal endometrial phenotype of abnormal uterine bleeding. Iron deficiency and iron deficiency anemia are closely associated with abnormal uterine bleeding, but are often underestimated and under-recognized. The International Federation of Gynecology and Obstetrics has established standardized terminology and classification system for abnormal uterine bleeding, facilitating future research, diagnosis, and clinical management. Emerging technologies are providing new insights into the biology of the endometrium in health and disease and presenting new diagnostic and management approaches.