The focus often rests on maternal mortality, which is the death of a woman during pregnancy or shortly after. However, an equally important and far more common indicator of systemic failures in healthcare is Severe Maternal Morbidity (SMM). This measure shifts the perspective from death to life-threatening complications, offering a broader view of the safety and quality of maternity care. Focusing on SMM provides actionable data to identify and address weaknesses within the health system.
Defining Severe Maternal Morbidity
Severe Maternal Morbidity is formally defined by the U.S. Centers for Disease Control and Prevention (CDC) as unexpected outcomes of labor and delivery that result in significant short- or long-term consequences to a woman’s health. This definition captures serious illnesses that occur from conception through 42 days postpartum. The concept of SMM is closely linked to “maternal near miss,” which refers to a woman who nearly dies but survives a complication during pregnancy, childbirth, or the puerperium. SMM acts as the key public health metric for surveillance of these severe complications.
Clinical Conditions That Define SMM
SMM is identified through a specific list of 21 medical events and procedures that signal a severe complication or necessary life-saving intervention. These indicators are based on International Classification of Diseases (ICD) codes found in administrative hospital discharge data used for surveillance.
The list includes both acute clinical diagnoses and specific critical care procedures. Examples of severe diagnoses include disseminated intravascular coagulation (DIC), eclampsia, acute respiratory distress syndrome (ARDS), and sepsis. Other life-threatening conditions captured are acute renal failure, amniotic fluid embolism, and cardiac arrest.
Certain critical medical interventions are also included as standalone indicators because they represent treatment for a potentially fatal condition. These procedures include receiving a massive blood transfusion (typically four or more units of blood products). An unanticipated hysterectomy performed during or immediately following delivery, or the need for temporary ventilation, also classifies the event as SMM.
Tracking and Measuring SMM
Public health surveillance methods monitor the incidence of SMM across the population. Data is primarily collected from administrative hospital discharge records, which contain the ICD codes necessary to identify the 21 SMM indicators. This allows for a standardized, population-level assessment of severe complications.
The national incidence rate is calculated by determining the number of SMM events per 10,000 deliveries. In 2020, the national rate was approximately 88.2 SMM events per 10,000 deliveries, a figure that has been steadily increasing in recent years. Tracking SMM is an essential tool for assessing the quality of maternity care. Because SMM events are 50 to 100 times more common than maternal death, they provide a robust data set for identifying areas of concern and evaluating safety initiatives.
Key Demographic Disparities in SMM
The burden of Severe Maternal Morbidity is not equally distributed across all populations in the United States. Significant disparities are observed when SMM rates are analyzed by race, ethnicity, age, and geographic location. Non-Hispanic Black women experience SMM at a rate that is more than twice that of non-Hispanic white women, reflecting unequal outcomes across the country.
American Indian and Alaska Native women also face elevated rates of SMM, highlighting a persistent health inequity. SMM rates tend to peak at the extremes of maternal age, with the highest incidence seen in women aged 40 and older, and higher rates also observed in very young mothers. Geographic location and socioeconomic status also contribute to the unequal distribution, with higher rates reported in certain regions and among lower-income communities.