Pregnancy mortality risk much higher for blacks.
The pregnancy-related mortality ratio (PRMR), which is the number of pregnancy-related deaths per 100,000 live births, was 14.4 overall, and ranged from 12 in 1999 to 15 in 2004, for a total of 4,058 reported deaths, Dr. Cynthia J. Berg reported in a poster at the annual meeting of the Society for Pediatric and Perinatal Epidemiologic Research.
One-fourth of maternal deaths were related to medical conditions, including chronic diseases such as hypertension and other cardiovascular diseases, said Dr. Berg, a medical epidemiologist in the CDC's Division of Reproductive Health. In addition, 13% were due to hemorrhage, 13% to hypertensive disorders of pregnancy, 12% to cardiomyopathy, 10% to infection, and 10% to pulmonary embolism.
The overall PRMR was 10.1 for white women and 37.3 for black women. The discrepancy, present since the 1940s, remains an important reproductive health issue, although the reasons for the difference still are not understood, Dr. Berg said in an interview.
"African American women are more likely to die of all the different causes of pregnancy-related death. The risk of a black woman dying from hemorrhage, infection, and embolism is essentially the same about four times greater than for white women and we don't know why," she said.
A CDC analysis of pregnancy related mortality data for 1991 1999 showed a PRMR of 30 for black women and 8.1 for white women (MMWR 2003; 52[SS02]:l-8). The overall PRMR has risen since 1986, when the CDC began collecting data on pregnancy deaths through the Pregnancy Mortality Surveillance System, according to Dr. Berg.
She said that the increase is likely due in part to improvements in reporting methods--including the growing number of states that now link death certificates of women of reproductive age to birth and fetal death certificates, and/or include check boxes on death certificates that indicate a temporal relationship between pregnancy and the death.
"As people become more aware of maternal mortality, they're more likely to report it, so our ascertainment has increased," she said, noting that since 2003, more and more states have included the check boxes on death certificates.
However, the growing number of women who are becoming pregnant past the age of 35, as well as the increase in obesity and body mass index in the general population--trends that are also reflected in the population of women who become pregnant--may have contributed to the increase in maternal mortality as well, Dr. Berg said.
Dr. Berg noted research conducted by the National Center for Health Statistics showing that in 1993, 10.4% of U.S. deliveries were to women aged 35 years and older, but that by 2005, that number had risen to 14.4%.
The present study revealed a two-, three-, and fourfold increase in pregnancy-related mortality resulting from cerebrovascular accident, medical conditions, and cardiomyopathy, respectively, between the periods 1991-1997 and 1998-2004.
A cerebrovascular accident is "a prime example of something with a causal relationship to pregnancy that frequently might not have been identified without either a data linkage [between birth and maternal death certificates] or a check box on the death certificate," said Dr. Berg.
Although the PRMR has increased, the proportion of deaths resulting from hemorrhage has decreased more than 50% since the period 1979 1986, Dr. Berg reported. Between 1979-1986 and 1998-2004, there was a sharp decline in the percentage of deaths associated with ectopic pregnancy. Advances in the identification and treatment of ectopic pregnancy and hemorrhage, including the use of ultrasound, medication, and embolization, may have contributed to this decrease, she said.
Although pregnancy-related mortality in the United States is relatively rare, the issue warrants ongoing study, in part because "it's much less common in many other countries," Dr. Berg said. "In 2005, we ranked 31st in the world in terms of maternal mortality, so there are many countries [for example, Canada. Australia, and Sweden] that have lower rates." Dr. Berg also pointed to research indicating that approximately 30%-40% of these pregnancy-related deaths could be prevented (Obstet. Gynecol. 2005;106:1228-34).
BY SUSAN BIRK
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|Publication:||OB GYN News|
|Date:||Aug 1, 2008|
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