(WOMENSENEWS)–Research on why women die in childbirth is very scarce.

One of the few looks at maternal mortality in the United States was New York City’s recent analysis of 161 women who died from 2001 to 2005.

It’s a small study with loud warning bells for African American women, who make up 24 percent of the city’s maternity population.

Fifty-eight percent of those who died of pregnancy-induced conditions in the study were black and 10 percent were white. Hispanic and Asian/Pacific Islander pregnant women died at twice the rate of white pregnant women, but at significantly lower rates than blacks.

Women over 40 were found to be about 2.6 times more likely to die from childbirth-related conditions than younger women. Forty-nine percent were obese. Pregnant women who had private insurance and those insured by Medicaid –government insurance for those with low incomes–had similar rates of pre-natal care.

The New York City report drew no conclusions about how to lower the city’s high rate of maternal deaths among African Americans.

Debra Bingham has some ideas.

She is vice president of research, education and publications of the Washington-based Association of Women’s Health, Obstetric and Neonatal Nurses, an association of 24,000 nurse clinicians, educators and executives who promote the health of women and newborns.

Bingham suggests examining the level of care that different women receive.

"Some women may have received too few interventions while others received too many," she said. "Some women may have had difficulty getting access to primary care and contraception, so they were more likely to have an unintended pregnancy and develop complications because their bodies hadn’t recovered from the previous birth."

More Follow-Up Care

In the United States 1 out of every 7 maternal deaths occurs six weeks after delivery, so some deaths might have been prevented if the woman received more follow-up care.

"On the other hand, some women may have received too many interventions," Bingham said. "Surgical interventions may have reached a level of overuse in the United States. Although there has been a 50 percent increase in the number of Cesarean sections since the 1990s, we have not seen any data to show that this leads to improvements in outcomes for the mother or baby. C-sections carry all the risks of abdominal surgery, such as infection and hemorrhage and life-long complications, such as adhesions."

The city’s report found that 79 percent of all mothers who died from pregnancy-related causes gave birth via C-section. Although the report did not break the C-section data down by race or ethnicity, it did note that C-sections were the most common method of delivery among women who died from hemorrhage, infections and embolism.

A national review of several obstetrical studies from 1998 to 2005 found significant increases in the rate of pulmonary embolism (blood clots that form in the legs and travel to the lung) among women who had C-sections. Other risk factors for embolisms were advanced maternal age, obesity and prolonged bed rest.

In the New York study, of the 28 women who died of embolism, 82 percent were African American, 24 percent were Hispanic and 4 percent were Asian. No white women died of embolism. Seventy-two percent of embolism deaths occurred either shortly before the birth or within one day of the end of pregnancy.

"Prompt diagnosis and therapy are extremely important in preventing deaths from embolism," said Bingham. "Many patients have non-specific signs. Anti-coagulant drugs and compression devices can make a big difference. Most patients who die do so within the first few hours. But in those who survive, a second incident often occurs."

The Atlanta-based Centers for Disease Control and Prevention (CDC) estimates that 17 percent of maternal deaths due to pulmonary embolism are preventable. Studies in other medical specialties indicate that embolism following surgery has been reduced by about 70 percent by using either compression devices or anti-coagulant drugs.

However, a 2008 study in the American Journal of Obstetrics and Gynecology, which examined maternal deaths in a group of hospitals, found that none of the nine women who died of pulmonary embolism had received compression devices or medications.

C-Section Risks

In addition to pulmonary embolism, C-sections also increase the risk of dying of infections. A CDC study found that women who have C-sections have five times the risk of infections as those who have vaginal births.

Black women had the highest rate of deaths from infections in the New York study: 48 percent, compared to 26 percent for Hispanics, 13 percent for whites and 13 percent for Asian.

The New York study also found that 65 percent of women who died of pregnancy-induced hypertension were African American, while 4 percent were white.

Twenty-two percent of the women who died of pregnancy-induced hypertension were Hispanic and 9 percent were Asian.

"This finding shows that the medical community must do a better job of managing hypertension among African American women before, during and after delivery because African Americans are more likely to have hypertension, develop it at earlier ages and have substantially elevated pressures," said Dr. Franklyn H. Geary Jr., professor and director of the division of maternal fetal medicine of obstetrics at Morehouse School of Medicine in Atlanta, which encourages graduates to deliver health care to underserved populations.

Some studies have suggested that African Americans have a salt-sensitive gene that causes kidneys to retain sodium, which increases blood pressure.

Higher rates of obesity in African American women also contribute to hypertension.

But in the New York study, 44 percent of the white pregnant women who died were obese; 60 percent in the case of African Americans–an imbalance but not sufficient to explain the vast difference between the percentage of white women and African American women who die.

At the same time, this data suggest that obesity could be a bigger risk factor for black women and raises questions about whether the prenatal care they received was sufficient to overcome those risks.

"Obese African American women often need care by specialists in high risk obstetrics because they develop hypertension, gestational diabetes and other complications in pregnancy," said Geary. "Unfortunately, the communities where they live may lack such specialists."

More Prenatal Care Needed

African American women in general also may need more than the recommended 13 prenatal visits, so that nutrition, exercise and other ways of managing hypertension can be covered in depth, Geary added.

"Increasing the availability of child care and giving women time off of work for prenatal care also may decrease maternal mortality among African American women who lack these supports," he said.

An Illinois study found that black women who had high-risk pregnancies were four times more likely to die than were white women who had high-risk pregnancies.

Geary said that tailoring prenatal care to the special risk factors of African Americans will help reduce the risk of developing preeclampsia, a condition characterized by an abrupt increase in blood pressure, swelling of hands and face, leaking of protein in the urine and headaches.

The life-threatening condition affects only 3 to 5 percent of pregnant women, but some studies have found a three-fold increased risk among African Americans.

Research by Thelma Patrick, an assistant investigator at the Pittsburgh-based Magee-

Women’s Research Institute, found that black women have more severe forms and experience preeclampsia earlier in pregnancy, typically at six months.

African American women are also more likely to die from hemorrhages in childbirth. The New York study found that 44 percent of the women who died in hemorrhage were African Americans compared to 7 percent for whites, 33 percent for Hispanic and 15 percent for Asians.

"The most important thing to do is to identify the women who are at risk for hemorrhage, such as those who are pregnant with twins or triplets or have large babies that make it difficult for the uterus to contract," said Dr. Jeffrey C. King, chair of the maternal mortality special interest group of the American College of Obstetricians and Gynecologists, the Washington-based professional organization of physicians with advanced training in women’s health

Eighty-one percent of hemorrhage deaths in the New York study occurred either shortly before the birth or within one day of the end of pregnancy.

"Every minute counts in responding to hemorrhages, so being in a hospital that has the necessary resources is also important," said King, who specializes in high-risk obstetrics at the University of Louisville in Kentucky. "Almost 50 percent of deaths that occur because of hemorrhages take place in hospitals that deliver less than 500 babies a year. If you are a mother in a small hospital that has only a few units of blood on hand and has to get additional supplies from somewhere else, you can die."

American College of Obstetricians and Gynecologists chapters in New York and other states have assisted hospitals in developing protocols to ensure rapid response to hemorrhages and other obstetrical emergencies.

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Sharon Johnson is a New York-based freelance writer.

For more information:

American College of Obstetricians and Gynecologists:

Association of Women’s Health, Obstetric and Neonatal Nurses: