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Pregnancy Mortality Surveillance System

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

CDC initiated national surveillance of pregnancy-related deaths in 1986 in response to the limitations in vital records for surveillance of maternal deaths and because more clinical information was needed about causes of maternal death.

How does CDC define pregnancy-related deaths?

For reporting purposes, a pregnancy-related death is defined as the death of a woman while pregnant or within 1 year of pregnancy termination—regardless of the 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 D.C.) 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 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 health of a nation. 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.

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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 a high of 17.8 deaths per 100,000 live births in 2009. 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 from 1987 to 2009 (the latest available year of data).

 

Trends in Pregnancy–Related Mortality in the United States, 1987–2009

Trends in Pregnancy–Related Mortality in the United States, 1987–2008. This line graph represents the number of pregnancy-related deaths per 100,000 live births per year: 1987, 7.2; 1988, 9.4; 1989, 9.8; 1990, 10.0; 1991, 10.3; 1992, 10.8; 1993, 11.1; 1994, 12.9; 1995, 11.3; 1996, 11.3; 1997, 12.9; 1998, 12.0; 1999, 13.2; 2000, 14.5; 2001, 14.7; 2002, 14.1; 2003, 16.8; 2004, 15.2; 2005, 15.4; 2006, 15.7; 2007, 14.5; 2008, 15.5; 2009, 17.8.

The reasons for this increase in pregnancy-related mortality are unclear. The use of computerized data links by the states, changes in the way causes of death are coded, and the addition of a pregnancy checkbox to the death certificate in many states have likely improved identifying pregnancy-related deaths over time. Whether the actual risk of a woman dying from pregnancy-related causes has increased is unclear. Many studies show that an increasing number of pregnant women in the United States have chronic health conditions such as hypertension,1 diabetes,2 and chronic heart disease.3 These conditions may put a pregnant woman at higher risk of adverse outcomes.

The higher pregnancy-related mortality ratio in 2009 compared with previous years is caused by the 2009 H1N1 influenza pandemic, which affected a large number of pregnant women.4-6 Data from 2010 are not yet available, but we expect to see additional impact on the mortality ratio from pregnant women affected by the 2009–2010 influenza season. Although the overall risk of dying from pregnancy complications is low, some women are at a higher risk than others. Variability in the risk of death by race, ethnicity, and age indicates that more can be done to understand and reduce pregnancy-related deaths.7

Causes of and risk factors for pregnancy-related deaths from 1987 to 2005 have already been published in the literature.8-10 Key pregnancy-related mortality data for 2006–2009 (the latest data available) are summarized below.

In the United States,

  • Of the 6,848 deaths within a year of pregnancy termination that occurred from 2006 to 2009 and were reported to CDC, 2,689 were found to be pregnancy-related.
  • The pregnancy-related mortality ratio was 15.8 deaths per 100,000 live births for 2006–2009.
  • Considerable racial disparities in pregnancy-related mortality exist. During 2006–2009, the pregnancy-related mortality ratios were
    • 11.7 deaths per 100,000 live births for white women.
    • 35.6 deaths per 100,000 live births for black women.
    • 17.6 deaths per 100,000 live births for women of other races.

 

Causes of Pregnancy-Related Death in the United States, 2006–2009

Causes of Pregnancy-Related Death in the United States, 2006–2008. see data points below graph.

Note: Total does not add up to 100% because the cause of death is unknown for 5.3% of all pregnancy-related deaths.

Note: Noncardiovascular diseases, (e.g. infectious, respiratory, gastrointestinal, endocrine, hematologic), 11.9%.

This graph shows percentages of pregnancy-related deaths in the United States in 2006–2009 caused by

  • Cardiovascular diseases, 14.6%.
  • Infection/sepsis, 14.0%.
  • Noncardiovascular diseases, (e.g. infectious, respiratory, gastrointestinal, endocrine, hematologic), 11.9%.
  • Cardiomyopathy, 11.8%.
  • Hemorrhage, 11.0%.
  • Hypertensive disorders of pregnancy, 9.9%.
  • Thrombotic pulmonary embolism, 9.4%.
  • Cerebrovascular accidents, 6.1%.
  • Amniotic fluid embolism, 5.4%.
  • Anesthesia complications, 0.6%.

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References:

  1. Hypertensive disorders and severe obstetric morbidity in the United States: 1998–2006. Obstet Gynecol. 2009;113(6):1299–1306.
  2. Diabetes trends among delivery hospitalizations in the United States, 1994–2004. Diabetes Care. 2010;33(4):768–773.
  3. Chronic heart disease and severe obstetric morbidity among hospitalizations for pregnancy in the USA: 1995–2006. Br J Obstet Gynaecol. 2011;118(3):345–352.
  4. Severity of 2009 pandemic influenza A (H1N1) virus infection in pregnant women. Obstet Gynecol. 2010;115(4):717–726.
  5. Severe 2009 H1N1 influenza in pregnant and postpartum women in California. N Engl J Med. 2010;;362(1):27–35.
  6. Pandemic 2009 influenza A(H1N1) virus illness among pregnant women in the United States. JAMA. 2010;  21;303(15):1517–1525.
  7. Race, ethnicity and nativity differentials in pregnancy-related mortality in the United States: 1993–2006. Obstet Gynecol. 2012;120(2):261–268.
  8. Pregnancy-related mortality in the United States, 1987–1990. Obstet Gynecol. 1996;88:161–167.
  9. Pregnancy-related mortality in the United States, 1991–1997. Obstet Gynecol. 2003;101:289–296.
  10. Pregnancy-related mortality in the United States, 1998–2005. Obstet Gynecol. 2010;116:1302–1309.
 

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