Pregnancy Mortality Surveillance System
14 Oct 2022About the Pregnancy Mortality Surveillance System (PMSS)
CDC conducts national pregnancy-related mortality surveillance to better understand the risk factors for and causes of pregnancy-related deaths in the United States. The Pregnancy Mortality Surveillance System (PMSS) defines a pregnancy-related death as a death while pregnant or within 1 year of the end of pregnancy from any cause related to or aggravated by the pregnancy. Medical epidemiologists review and analyze death records, linked birth records and fetal death records if applicable, and additional available data from all 50 states, New York City, and Washington, DC. PMSS is used to calculate the pregnancy-related mortality ratio, an estimate of the number of pregnancy-related deaths for every 100,000 live births. The birth data used to calculate pregnancy-related mortality ratios were obtained from the National Vital Statistics System (NVSS) via the Centers for Disease Control and Prevention, Wide-ranging Online Data for Epidemiologic Research (CDC WONDER).
Trends in Pregnancy-Related Deaths
ince the Pregnancy Mortality Surveillance System was implemented, the number of reported pregnancy-related deaths in the United States increased from 7.2 deaths per 100,000 live births in 1987 to 17.6 deaths per 100,000 live births in 2019. The graph above shows trends in pregnancy-related mortality ratios between 1987 and 2019 (the latest available year of data).
The reasons for the overall increase in pregnancy-related mortality are unclear. Identification of pregnancy-related deaths has improved over time due to the use of computerized data linkages between death records and birth and fetal death records by states, changes in the way causes of death are coded, and the addition of a pregnancy checkbox to death records. However, errors in reported pregnancy status on death records have been described, potentially leading to overestimation of the number of pregnancy-related deaths.
Pregnancy-Related Deaths by Race/Ethnicity
Considerable racial/ethnic disparities in pregnancy-related mortality exist.2,3 During 2017–2019, the pregnancy-related mortality ratios (PRMRs) were:
- 62.8 deaths per 100,000 live births among non-Hispanic Native Hawaiian or Other Pacific Islander persons.
- 39.9 deaths per 100,000 live births among non-Hispanic Black persons.
- 32.0 deaths per 100,000 live births among non-Hispanic American Indian or Alaska Native persons.
- 14.1 deaths per 100,000 live births among non-Hispanic White persons.
- 12.8 deaths per 100,000 live births among non-Hispanic Asian persons.
- 11.6 deaths per 100,000 live births among Hispanic persons.
Race or ethnicity was missing for 1.4% of pregnancy-related deaths in 2017-2019.
In 2018-2019, the PRMR was 7.1 deaths per 100,000 live births among non-Hispanic multiple race persons.
PRMRs were not calculated for persons who identified as non-Hispanic Other Race, because PRMRs based on counts less than 8 are considered not reliable for reporting. Variability in the risk of death by race/ethnicity may be due to several factors including access to care, quality of care, prevalence of chronic diseases, structural racism, and implicit biases.
Causes of Pregnancy-Related Deaths
The graph above shows percentages of pregnancy-related deaths in the United States during 2017–2019 caused by:
- Other cardiovascular conditions, 14.5%.
- Infection or sepsis, 14.3%.
- Cardiomyopathy, 12.1%.
- Hemorrhage, 12.1%.
- Thrombotic pulmonary or other embolism, 10.5%.
- Hypertensive disorders of pregnancy, 6.3%.
- Amniotic fluid embolism, 6.1%.
- Cerebrovascular accidents, 5.8%.
- Anesthesia complications, 0.2%.
- Other noncardiovascular medical conditions, 11.1%.
The cause of death is unknown for 7.0% of all 2017-2019 pregnancy-related deaths.
Studies show that an increasing number of pregnant persons in the United States have chronic health conditions such as hypertension, diabetes, and chronic heart disease. These conditions may put a person at higher risk of complications during pregnancy or in the year postpartum.
Pregnancy-Related Deaths by Urban-Rural Classifications
The graph above shows the pregnancy-related mortality ratios (PRMRs) by urban-rural classifications using the 2013 National Center for Health Statistics Urban-Rural Classification Scheme for Counties . Data were geocoded using the Texas A&M Geoservices’ Batch Geocoding. Metropolitan counties (i.e., large central, large fringe, medium, and small) can be considered urban, and micropolitan and noncore counties as rural. During 2017-2019, the PRMRs were:
- 15.9 deaths per 100,000 live births for persons living in large central metro counties.
- 14.0 deaths per 100,000 live births for persons living in large fringe metro counties.
- 17.0 deaths per 100,000 live births for persons living in medium metro counties.
- 18.6 deaths per 100,000 live births for persons living in small metro counties.
- 21.8 deaths per 100,000 live births for persons living in micropolitan counties.
- 26.1 deaths per 100,000 live births for persons living in noncore counties.
Urban-rural classification was missing or unknown for 2.4% of pregnancy-related deaths in 2017-2019.
A prior study found that PRMRs were higher in noncore (the most rural categorization) counties when compared to metropolitan counties.11 Variability in the risk of death by geographic location groups might reflect chronic health conditions and access to care (e.g., rural residents may face challenges such as distance from and lack of access to obstetric services and providers) including risk-appropriate care.
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