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 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 linkages. All the information obtained is summarized, and medically-trained epidemiologists make a determination as to the cause and time of death related to the pregnancy. Causes of death are coded 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.

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 16.8 deaths per 100,000 live births in 2003, and declined slightly to 15.5 deaths per 100,000 live births in 2008. 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 2008 (the latest available year of data).

Trends in Pregnancy-Related Mortality in the United States, 1987–2008

The reasons for this increase in pregnancy-related mortality are unclear. 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 in many states have likely improved identifying pregnancy-related deaths over time. 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.¹ Many studies show that an increasing number of pregnant women in the United States have chronic health conditions such as hypertension,² diabetes,³ and chronic heart disease.⁴ These conditions may put a pregnant woman at higher risk of adverse outcomes.

Causes of and risk factors for pregnancy-related deaths between 1987 and 2005 have already been published in the literature.^5–7 Key pregnancy-related mortality data for 2006–2008 (the latest data available) are summarized below.

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In the United States—

• Of the 5,001 deaths within a year of pregnancy termination that occurred between 2006 and 2008 and were reported to CDC, 1,953 were found to be pregnancy-related.
• The pregnancy-related mortality ratio was 15.2 deaths per 100,000 live births for the period 2006–2008.
• Considerable racial disparities in pregnancy-related mortality exist. During the 2006–2008 period, the pregnancy-related mortality ratios were—
• 11.3 deaths per 100,000 live births for white women.
• 34.8 deaths per 100,000 live births for black women.
• 14.5 deaths per 100,000 live births for women of other races.

Causes of Pregnancy-Related Death in the United States, 2006–2008

Note: Total does not add up to 100% because the cause of death is unknown for 5.5% of all pregnancy-related deaths.

This graph shows percentages of pregnancy-related deaths in the United States in 2006–2008 caused by—

• Cardiovascular Diseases, 14.6%
• Cardiomyopathy, 12.4%
• Non-Cardiovascular Diseases, 11.9%
• Hemorrhage, 11.5%
• Infection/Sepsis, 11.1%
• Hypertensive Disorders of Pregnancy, 10.5%
• Thrombotic Pulmonary Embolism, 10.3%,
• Amniotic Fluid Embolism, 5.9%
• Cerebrovascular Accidents, 5.7%
• Anesthesia Complications, 0.6%

The cause of death is unknown for 5.5% of all 2006–2008 pregnancy-related deaths.

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References:

1. Creanga AA, Berg CJ, Syverson C, Seed K, Bruce C, Callaghan WM. Race, ethnicity and nativity differentials in pregnancy-related mortality in the United States: 1993–2006. Obstet Gynecol. 2012;120(2):261–268.
2. Kuklina EV, Ayala C, Callaghan WM. Hypertensive disorders and severe obstetric morbidity in the United States: 1998–2006. Obstet Gynecol. 2009;113(6):1299–1306.
3. Albrecht SS, Kuklina EV, Bansil P et al. Diabetes trends among delivery hospitalizations in the United States, 1994–2004. Diabetes Care. 2010;33(4):768–773.
4. 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(3):345–352.
5. Berg CJ, Atrash HK, Koonin LM, Tucker M. Pregnancy-related mortality in the United States, 1987–1990. Obstet Gynecol. 1996;88:161–167.
6. Berg CJ, Chang J, Callaghan WM, Whitehead SJ. Pregnancy-related mortality in the United States, 1991–1997. Obstet Gynecol. 2003;101:289–296.
7. Berg CJ, Callaghan WM, Syverson C, Henderson Z. Pregnancy-related mortality in the United States, 1998–2005. Obstet Gynecol. 2010;116:1302–1309.