Pregnancy Mortality Surveillance System

When did CDC start conducting national surveillance of pregnancy-related deaths?

CDC initiated national surveillance of pregnancy-related deaths in 1986 because more clinical information was needed to fill data gaps about causes of maternal death.

How does CDC define pregnancy-related deaths?

A pregnancy-related death is defined as the death of a woman while pregnant or within 1 year of the end of a pregnancy –regardless of the outcome, duration or site of the pregnancy–from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes.

How are the data collected and coded?

Each year, CDC requests the 52 reporting areas (50 states, New York City, and Washington DC) to voluntarily send copies of death certificates for all women who died during pregnancy or within 1 year of pregnancy, and copies of the matching birth or fetal death certificates, if they have the ability to perform such record links. All of the information obtained is summarized, and medically trained epidemiologists determine the cause and time of death related to the pregnancy. Causes of death are coded by using a system established in 1986 by the American College of Obstetricians and Gynecologists and the Centers for Disease Control and Prevention Maternal Mortality Study Group.

How are the data used?

Data are analyzed by CDC scientists. Information about causes of pregnancy-related deaths and risk factors associated with these deaths is released periodically through peer-reviewed literature, CDC’s Morbidity and Mortality Weekly Reports, and the CDC Web site. This information helps clinicians and public health professionals to better understand circumstances surrounding pregnancy-related deaths and to take appropriate actions to prevent them.

How is data confidentiality protected?

Pregnancy mortality surveillance data are protected under 308(d) Assurance of Confidentiality. Because of this Assurance, all data and documents are considered confidential materials and are safeguarded to the greatest extent possible. This Assurance extends to all pregnancy mortality surveillance data obtained from individual states and reporting areas.

What is the pregnancy-related mortality ratio?

The pregnancy-related mortality ratio is an estimate of the number of pregnancy-related deaths for every 100,000 live births. This ratio is often used as an indicator to measure the nation’s health. Factors that affect the health of the entire population can also affect mortality among pregnant and postpartum women.

The pregnancy-related mortality ratio fell significantly in the United States during the 20th century. This historic decline was because of medical and technological advances. Interest and concern at the local, state, and federal levels for why pregnancy-related deaths occur led to the development of systems for identifying, reviewing, and analyzing pregnancy-related deaths.

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 16.9 deaths per 100,000 live births in 2016. The graph below shows trends in pregnancy-related mortality ratios defined as the number of pregnancy-related deaths per 100,000 live births in the United States between 1987 and 2016 (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 by the states, changes in the way causes of death are coded, and the addition of a pregnancy checkbox to the death certificate. However, errors in reported pregnancy status on death certificates 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.

Considerable racial/ethnic disparities in pregnancy-related mortality exist.2,3 During 2011–2016, the pregnancy-related mortality ratios were:

  • 42.4 deaths per 100,000 live births for black non-Hispanic women.
  • 30.4 deaths per 100,000 live births for American Indian/Alaskan Native non-Hispanic women.
  • 14.1 deaths per 100,000 live births for Asian/Pacific Islander non-Hispanic women.
  • 13.0 deaths per 100,000 live births for white non-Hispanic women.
  • 11.3 deaths per 100,000 live births for Hispanic women.

Variability in the risk of death by race/ethnicity indicates that more can be done to understand and reduce pregnancy-related deaths.

Studies show that an increasing number of pregnant women in the United States have chronic health conditions such as hypertension,4,5 diabetes,5-8 and chronic heart disease.9,10 These conditions may put a pregnant woman at higher risk of pregnancy complications. While the contribution of hemorrhage, hypertensive disorders of pregnancy (i.e., preeclampsia, eclampsia), and anesthesia complications to pregnancy-related deaths have declined, the contribution of cardiovascular, cerebrovascular accidents, and other medical conditions have increased.9 When combined, cardiovascular conditions (i.e., cardiomyopathy, other cardiovascular conditions, cerebrovascular accidents) were responsible for greater than one-third of pregnancy-related deaths in 2011–2016.

Causes of and risk factors for pregnancy-related deaths between 1987 and 2013 have been published.11-15 The graph below shows percentages of pregnancy-related deaths in the United States during 2011–2016 caused by:

  • Hemorrhage, 11.0%.
  • Infection or sepsis, 12.5%.
  • Amniotic fluid embolism, 5.6%.
  • Thrombotic pulmonary or other embolism, 9.0%.
  • Hypertensive disorders of pregnancy, 6.9%.
  • Anesthesia complications, 0.3%.
  • Cerebrovascular accidents, 7.7%.
  • Cardiomyopathy, 11.0%.
  • Other cardiovascular conditions, 15.7%.
  • Other noncardiovascular medical conditions, 13.9%.

The cause of death is unknown for 6.4% of all 2011–2016 pregnancy-related deaths.

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. Kuklina EV, Ayala C, Callaghan WM. Hypertensive disorders and severe obstetric morbidity in the United States: 1998–2006. Obstet Gynecol. 2009;113:1299–1306.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. Creanga AA, Syverson C, Seed K, Callaghan WM. Pregnancy-related mortality in the United States, 2011–2013. Obstet Gynecol. 2017;130:366–373.
  12. Berg CJ, Atrash HK, Koonin LM, Tucker M. Pregnancy-related mortality in the United States, 1987–1990. Obstet Gynecol. 1996;88:161–167.
  13. Berg CJ, Chang J, Callaghan WM, Whitehead SJ. Pregnancy-related mortality in the United States, 1991–1997. Obstet Gynecol. 2003;101:289–296.
  14. Berg CJ, Callaghan WM, Syverson C, Henderson Z.  Pregnancy-related mortality in the United States, 1998–2005. Obstet Gynecol. 2010;116:1302–1309.
  15. 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.