ABSTRACT
There is broad consensus that measuring severe maternal morbidity (SMM) is critical to improving maternal health. Despite 50 years of effort by national, international, and professional organizations, determining the ideal SMM measure remains a work in progress. Various SMM measures have been proposed and evolved to fulfill different purposes: population surveillance, hospital-level trends and comparisons, and case reviews for quality improvement. This review examines definitions, strengths, limitations and challenges in data collection for the most-used SMM measures. Also discussed are proposals to expand these measures to include postpartum complications, mental health, and substance use disorders. Regardless of the challenges with definition and data collection, SMM measures are widely used and have become integral to improvement efforts at hospital, state, and national levels in the United States. We anticipate that available measures will continue to evolve to meet the needs of hospital systems and national surveillance moving forward.