Pregnancy Mortality Surveillance System

About the Pregnancy Mortality Surveillance System (PMSS)

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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 the death of a woman 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

Since the Pregnancy Mortality Surveillance System was implemented, the number of reported pregnancy-related deaths in the United States steadily increased from 7.2 deaths per 100,000 live births in 1987 to 17.3 deaths per 100,000 live births in 2018. The graph above shows trends in pregnancy-related mortality ratios between 1987 and 2018 (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.1 Whether the actual risk of a woman dying from pregnancy-related causes has increased is unclear, and in recent years, the pregnancy-related mortality ratios have been relatively stable.

Pregnancy-Related Deaths by Race/Ethnicity

Considerable racial/ethnic disparities in pregnancy-related mortality exist.2,3 During 2016–2018, the pregnancy-related mortality ratios (PRMRs) were:

  • 41.4 deaths per 100,000 live births for non-Hispanic Black persons.
  • 26.5 deaths per 100,000 live births for non-Hispanic American Indian or Alaska Native persons.
  • 14.1 deaths per 100,000 live births for non-Hispanic Asian or Pacific Islander persons.
  • 13.7 deaths per 100,000 live births for non-Hispanic White persons.
  • 11.2 deaths per 100,000 live births for Hispanic persons.

In 2018, the PRMR was 9.5 deaths per 100,000 live births for non-Hispanic multiple race persons.

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.4-6

Causes of Pregnancy-Related Deaths

The graph above shows percentages of pregnancy-related deaths in the United States during 2016–2018 caused by:

  • Other cardiovascular conditions, 16.2%.
  • Infection or sepsis, 13.9%.
  • Cardiomyopathy, 12.5%.
  • Hemorrhage, 11.0%.
  • Thrombotic pulmonary or other embolism, 9.4%.
  • Cerebrovascular accidents, 7.0%.
  • Hypertensive disorders of pregnancy, 6.8%.
  • Amniotic fluid embolism, 5.7%.
  • Anesthesia complications, 0.2%.
  • Other noncardiovascular medical conditions, 11.4%.

The cause of death is unknown for 6.0% of all 2016–2018 pregnancy-related deaths.

While the contributions of hemorrhage, hypertensive disorders of pregnancy (i.e., preeclampsia, eclampsia), and anesthesia complications to pregnancy-related deaths declined, the contributions of cardiovascular, cerebrovascular accidents, and other medical conditions increased.7 Studies show that an increasing number of pregnant persons in the United States have chronic health conditions such as hypertension,8,9 diabetes,9-12 and chronic heart disease.7,13 These conditions may put a person at higher risk of complications during pregnancy or in the year postpartum. Causes of and risk factors for pregnancy-related deaths between 1987 and 2016 have been published.2-3, 14-18

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 [PDF – 3 MB]. Metropolitan counties (i.e., large central, large fringe, medium, and small) can be considered urban, and micropolitan and noncore counties as rural. During 2016-2018, the PRMRs were:

  • 15.7 deaths per 100,000 live births for persons living in large central metro counties.
  • 13.8 deaths per 100,000 live births for persons living in large fringe metro counties.
  • 16.3 deaths per 100,000 live births for persons living in medium metro counties.
  • 17.9 deaths per 100,000 live births for persons living in small metro counties.
  • 19.5 deaths per 100,000 live births for persons living in micropolitan counties.
  • 24.4 deaths per 100,000 live births for persons living in noncore counties.

A prior study found that PRMRs were higher in noncore (the most rural categorization) counties when compared to metropolitan counties.19 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.20-21

Frequently Asked Questions

References

  1. Baeva S, Saxton DL, Ruggiero K, et al. Identifying maternal deaths in Texas using an enhanced method, 2012. Obstet Gynecol. 2018;131:762–769.
  2. Petersen EE, Davis NL, Goodman D, et al. Racial/ethnic disparities in pregnancy-related deaths — United States, 2007–2016. MMWR Morb Mortal Wkly Rep. 2019;68:762–765.
  3. Petersen EE, Davis NL, Goodman D, Cox S, Mayes N, Johnston E, Syverson C, Seed K, Shapiro-Mendoza CK, Callaghan WM, Barfield W. Vital signs: Pregnancy-related deaths, United States, 2011–2015, and strategies for prevention, 13 states, 2013–2017. MMWR Morb Mortal Wkly Rep. 2019;68:423–429.
  4. Bailey ZD, Krieger N, Agénor M, Graves J, Linos N, Bassett MT. Structural racism and health inequities in the USA: evidence and interventions. Lancet. 2017;389(10077):1453-1463. doi:10.1016/S0140-6736(17)30569-X
  5. Howell EA. Reducing disparities in severe maternal morbidity and mortality. Clin Obstet Gynecol 2018;61:387–99. https://doi.org/10.1097/GRF.0000000000000349.
  6. Hall WJ, Chapman MV, Lee KM, et al. Implicit racial/ethnic bias among health care professionals and its influence on health care outcomes: a systematic review. Am J Public Health 2015;105:e60–76. https://doi. org/10.2105/AJPH.2015.302903
  7. Kuklina EV, Callaghan WM. Chronic heart disease and severe obstetric morbidity among hospitalizations for pregnancy in the USA: 1995–2006. Br J Obstet Gynaecol. 2011;118:345–352.
  8. Kuklina EV, Ayala C, Callaghan WM. Hypertensive disorders and severe obstetric morbidity in the United States: 1998–2006. Obstet Gynecol. 2009;113:1299–1306.
  9. Admon LK, Winkelman TNA, Moniz MH, Davis MM, Heisler M, Dalton VK. Disparities in chronic conditions among women hospitalized for delivery in the United States, 2005–2014. Obstet Gynecol.2017;130(6):1319–1326.
  10. Albrecht SS, Kuklina EV, Bansil P, et al. Diabetes trends among delivery hospitalizations in the United States, 1994–2004. Diabetes Care.2010;33:768–773
  11. Correa A, Bardenheier B, Elixhauser A, Geiss LS, Gregg E. Trends in prevalence of diabetes among delivery hospitalizations, United States, 1993–2009. Matern Child Health J. 2015;19(3):635–642.
  12. Deputy NP, Kim SY, Conrey EJ, Bullard KM. Prevalence and changes in preexisting diabetes and gestational diabetes among women who had a live birth—United States, 2012–2016. MMWR Morb Mortal Wkly Rep.2018;67:1201–1207.
  13. Lima FV, Yang J, Xu J, Stergiopoulos K. National trends and in-hospital outcomes in pregnant women with heart disease in the United States.  Am J Cardiol. 2017; 119(10):1694-1700.
  14. Creanga AA, Syverson C, Seed K, Callaghan WM. Pregnancy-related mortality in the United States, 2011–2013. Obstet Gynecol.2017;130:366–373.
  15. Berg CJ, Atrash HK, Koonin LM, Tucker M. Pregnancy-related mortality in the United States, 1987–1990. Obstet Gynecol.1996;88:161–167.
  16. Berg CJ, Chang J, Callaghan WM, Whitehead SJ. Pregnancy-related mortality in the United States, 1991–1997. Obstet Gynecol.2003;101:289–296.
  17. Berg CJ, Callaghan WM, Syverson C, Henderson Z.  Pregnancy-related mortality in the United States, 1998–2005. Obstet Gynecol. 2010;116:1302–1309.
  18. Creanga AA, Berg CJ, Syverson C, Seed K, Bruce C, Callaghan WM. Pregnancy-related mortality in the United States, 2006–2010. Obstet Gynecol.2015;125:5–12.
  19. Merkt PT, Kramer MR, Goodman DA, Brantley MD, Barrera CM, Eckhaus L, Petersen EE. Urban-rural differences in pregnancy-related deaths, United States, 2011-2016. Am J Obstet Gynecol. 2021;225:183.e1-16.
  20. Hung P, Henning-Smith CE, Casey MM, Kozhimannil KB. Access to obstetric services in rural counties still declining, with 9 percent losing services, 2004-14. Health Aff. 2017;36(9):1663-1671.
  21. Xierali IM, Nivet MA, Rayburn WF. Relocation of obstetrician-gynecologists in the United States, 2005-2015. Obstet Gynecol. 2017;129(3):543-550.