Severe maternal morbidity (SMM) refers to unexpected, life-threatening complications during labor, delivery, or the postpartum period that result in significant short- or long-term consequences to a woman’s health. These are sometimes called “near miss” events, situations where a birthing person comes close to dying but survives. In the United States, SMM affects roughly 50,000 to 60,000 women each year. For every maternal death, there are 70 to 80 cases of severe illness, making SMM a far more common measure of danger in childbirth than mortality statistics alone reveal.
How SMM Differs From Maternal Mortality
Maternal mortality counts deaths during or shortly after pregnancy. It is a critical indicator, but it captures only the most extreme outcomes. About 650 to 750 women die from pregnancy-related causes in the U.S. each year. SMM captures a much larger group: the tens of thousands of women who survive serious complications but whose health is significantly harmed in the process. Tracking SMM gives hospitals and public health systems a broader, more actionable picture of where care is breaking down. A hospital might see very few maternal deaths in a given year but dozens of SMM cases, each one a signal that something went wrong during the birth process.
What Counts as Severe Maternal Morbidity
The CDC uses a standardized list of 21 indicators to identify SMM cases from hospital records. These indicators cover a range of organ failures, emergency interventions, and life-threatening diagnoses that occur during a delivery hospitalization. The most common ones include:
- Blood transfusion (receiving four or more units of blood), which is by far the most frequently flagged indicator
- Eclampsia, a dangerous escalation of high blood pressure that causes seizures
- Acute kidney failure
- Respiratory distress syndrome, where the lungs fail to exchange oxygen properly
- A blood clotting disorder called disseminated intravascular coagulation, where the body’s clotting system breaks down
- Heart failure or cardiac arrest
- Stroke or other cerebrovascular events
- Amniotic fluid embolism, a rare but often fatal condition where amniotic fluid enters the bloodstream
- Emergency hysterectomy
Other indicators on the CDC’s list include heart attack, aneurysm, and the need for emergency procedures to restore heart rhythm. When a delivery hospitalization triggers any one of these 21 indicators in the medical record, it is classified as an SMM event. The American College of Obstetricians and Gynecologists has also recommended that hospitals use two specific criteria as initial screening tools: receiving four or more units of blood, and admission to the ICU.
Most Common Underlying Causes
Two conditions drive the majority of SMM cases worldwide: severe bleeding (obstetric hemorrhage) and hypertensive disorders like preeclampsia and eclampsia. In surveillance data, hemorrhage accounts for roughly 65% of SMM cases, and hypertensive conditions account for about 22%. The remaining cases involve infections, blood clots, heart problems, and complications from anesthesia or surgery.
Hemorrhage can happen when the uterus doesn’t contract properly after delivery, when the placenta separates too early, or when there are tears in the birth canal. Hypertensive disorders involve dangerously high blood pressure that can damage the kidneys, liver, and brain. Eclampsia, the most severe form, causes seizures and can be fatal without rapid treatment. Both hemorrhage and hypertensive emergencies can escalate within minutes, which is why hospital preparedness is a major focus of prevention efforts.
Racial and Ethnic Disparities
SMM does not affect all groups equally. Nationally, rates of severe maternal morbidity are 1.6 times higher for Black birthing people and 1.2 times higher for Latinx birthing people compared to White birthing people. In some geographic areas, these gaps are even wider. The disparities reflect a combination of factors: differences in access to quality care, higher rates of chronic conditions like hypertension and diabetes, the cumulative effects of racism-related stress on the body, and documented patterns of medical providers being slower to respond to pain or warning signs in Black patients. These are systemic issues, not individual ones, and they persist even after accounting for income, education, and insurance status.
Long-Term Health Effects
SMM is not just an acute event. Women who survive it face elevated health risks for years afterward. A cohort study published in BJOG found that women who experienced SMM had four times the risk of developing cardiovascular disease and roughly twice the risk of endocrine disorders (like thyroid problems or diabetes) compared to women who delivered without complications. They were also nearly five times more likely to be hospitalized within the first year after delivery for any reason, and about twice as likely to be hospitalized in the years that followed.
Beyond physical health, survivors of SMM commonly report diminished quality of life, impaired sexual function, and psychological effects including post-traumatic stress, anxiety, and depression. For some women, the experience of nearly dying during what was expected to be a routine delivery is profoundly disorienting. Many describe feeling dismissed or confused about what happened to them, especially if the emergency unfolded quickly and was not clearly explained afterward. The need for ongoing follow-up care, both physical and psychological, is significant but often unmet.
How Hospitals Are Working to Reduce SMM
The Alliance for Innovation on Maternal Health (AIM), supported by the federal Health Resources & Services Administration, has developed standardized “patient safety bundles” designed to reduce preventable SMM cases and maternal deaths. These bundles are sets of evidence-based practices that hospitals implement as a package rather than relying on individual clinicians to remember each step during an emergency.
Current AIM bundles address the most dangerous scenarios: obstetric hemorrhage, severe hypertension, cardiac conditions, and sepsis during pregnancy. They also cover systemic factors like reducing unnecessary cesarean births (which carry higher complication risks) and improving postpartum discharge planning. The core approach involves having emergency medications and equipment staged and ready before they’re needed, training staff to recognize warning signs early, running regular drills so teams can practice emergency responses, and ensuring clear communication across providers. Bundles for perinatal mental health and substance use disorder have also been developed to address complications that extend beyond the delivery room.
The emphasis on hemorrhage and hypertension bundles reflects where the biggest opportunities for prevention exist. Many hemorrhage deaths and SMM cases involve delays in recognizing blood loss or delays in starting treatment. Standardized protocols that trigger automatic responses at specific clinical thresholds help remove those delays from the equation.
Why SMM Is Increasing
SMM rates in the United States have been rising, and several factors contribute. The average age of first-time mothers has increased, and older maternal age carries higher risks for conditions like hypertension and gestational diabetes. Rates of obesity, chronic hypertension, and diabetes have also risen in the general population, meaning more people enter pregnancy with pre-existing conditions that raise the likelihood of complications. Cesarean delivery rates remain high, and each repeat cesarean increases the risk of placental abnormalities and surgical complications in future pregnancies.
Better detection also plays a role. As hospitals adopt more systematic screening and coding practices, some cases that previously went unrecorded are now being captured. But the clinical consensus is that the rise is not purely a measurement artifact. The underlying health of the birthing population is changing, and the healthcare system has not fully adapted to manage that shift.