Between 1998 and 2005, the aggregate pregnancy-related mortality ratio in the United States was 14.5 deaths per 100,000 live births.1 This ratio is higher than that for any other reported period in the previous 20 years and varies by race: The risk of death from pregnancy-related causes for black women is 3–4 times that for white women. Also, while the proportions of deaths attributable to hemorrhage and hypertensive disorders have decreased over time, the proportions attributable to medical conditions, particularly cardiovascular, have increased.
A death is considered to be pregnancy-related if it occurred within one year of pregnancy and was caused by a complication of pregnancy, a chain of events initiated by pregnancy or an unrelated condition aggravated by pregnancy. To identify pregnancy-related deaths and calculate the risk of death from pregnancy complications, researchers used data from the Centers for Disease Control and Prevention’s Pregnancy Mortality Surveillance System, along with data on live births from public-use natality files from the National Center for Health Statistics. The analysis included all 4,693 pregnancy-related deaths identified for 1998–2005.
During the eight-year span studied, the pregnancy-related mortality ratio for all women ranged from 12.0 deaths per 100,000 live births (in 1998) to 16.8 (in 2003); the aggregate ratio was 14.5 deaths per 100,000 live births. For white women, the aggregate ratio was 10.2; for black women, 37.5; and for women of other races, 13.4. Overall, the risk of pregnancy-related death among black women was 3–4 times as high as that among white women.
For all women, pregnancy-related mortality increased with age: Among white women, risk of death from pregnancy-related causes ranged from 6.1 deaths per 100,000 live births for women younger than 15 to 40.0 for those older than 39; this pattern was even more pronounced for black women and women of other races. Unmarried white women had a 40% higher risk of pregnancy-related death than white women who were married (12.5 vs. 9.2), though pregnancy-related mortality was unrelated to marital status among black women and women of other races. In general, risk of death caused by pregnancy complications increased with parity. Except among black women, the earlier prenatal care was started, the lower the risk of pregnancy-related death; in each racial or ethnic group, women who received any prenatal care had a lower risk than those who received none.
Seven causes were responsible for the majority of pregnancy-related deaths—thrombotic pulmonary embolism (a blockage in an artery of the lungs caused by a blood clot), 10%; cardiomyopathy (disease or weakening of the heart muscle) and infection, 11% each; cardiovascular conditions, hemorrhage and hypertensive disorders of pregnancy (preeclampsia and eclampsia), 12% each; and noncardiovascular medical conditions, 13%. The most common cause of death varied by the pregnancy outcome; for example, hemorrhage was the cause of death for 93% of women experiencing ectopic pregnancy, but for only 10% of women who had had a live birth. The proportions of deaths attributed to hemorrhage and hypertensive disorders showed a steady decline from 1987–1990 to 1998–2005, while the proportions attributed to cardiomyopathy, cardiovascular conditions and noncardiovascular conditions increased.
The researchers indicate that some of the increase in the pregnancy-related mortality ratio between 1998 and 2005 may be the result of improvements in the registration and classification of deaths that were made during this time period. They note that a limitation of their data is the voluntary nature of participation in the Pregnancy Mortality Surveillance System and acknowledge that these data lack the level of detail that could be obtained by state review committees. The researchers also note that the increase in pregnancy-related deaths caused by conditions not typically associated with pregnancy, such as cardiovascular conditions, speaks to the need for early identification and management of these conditions during a woman’s pregnancy. They conclude that to decrease pregnancy-related mortality, "understanding the social and health care contexts surrounding women who die as a result of pregnancy is critical to instituting the systemic changes needed."—L. Melhado