Tens of thousands of American women each year need emergency treatment such as blood transfusions to save their lives while they deliver their babies or immediately after. A new study shows about 1.6 percent of births involve such care.

The research also reveals how much a mother's racial and ethnic background — and her health before pregnancy — affects her risk of a life-threatening birth experience.

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It shows that women of color and those of Hispanic heritage had higher rates of severe birth-related health issues than non-Hispanic white women — even if they were otherwise healthy. Non-Hispanic black women, for instance, had a 70 percent higher rate of major birth problems than non-Hispanic white women.

Women of any race or ethnicity who had a health condition such as asthma, diabetes, depression or substance use issues before giving birth also had a higher risk of the same severe problems after giving birth.

Still, black and Hispanic women with two or more conditions were two to three times more likely to experience a severe birth problem compared with white mothers, the team of University of Michigan researchers found.

"Women of color who have multiple health conditions before they have their baby appear to experience a double-whammy effect," says Lindsay Admon, M.D., M.Sc., the study's lead author. "This should force us to think about how to structure care to best serve these vulnerable women — not only during pregnancy but before and after giving birth, too."

The new study in the journal Obstetrics & Gynecology shines a detailed spotlight on the issue of what physicians call severe maternal morbidity.

Examining disparities and health issues

Deaths among new mothers have received public attention in recent years, Admon notes. But far less data have been available on birth problems that could have killed the mother if emergency care wasn't given.

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The new study focuses on 10 types of maternal morbidity. Blood transfusions, used mainly in women suffering a serious hemorrhage, were the most common. They accounted for three-quarters of cases and most of the racial disparity.

And many scenarios are preventable.

"Situations like these are often considered near misses, and looking at them allows us to get a better picture of who the high-risk women really are," says Admon, an obstetrician at Michigan Medicine's Von Voigtlander Women's Hospital and a member of the U-M Institute for Healthcare Policy and Innovation.

"Celebrities like Serena Williams who have shared their birth-related emergency stories publicly have drawn the national spotlight to the urgent need to reduce racial and ethnic disparities in care for women around the time of delivery. To drive and target those changes, we need specific data like these."

Because many births are paid for by Medicaid, using state and federal funds, the findings also have importance for health policy.

In fact, the new study shows that Medicaid paid for nearly two-thirds of all births among women of non-Hispanic black, Hispanic and American Indian/Alaskan Native backgrounds. Medicaid also paid for more than a third of all births among non-Hispanic white women and those of Asian/Pacific Islander backgrounds.

More about the study

The researchers used anonymous national data about hospital stays from 2012 to 2015, during which 40,873 women who gave birth underwent an emergency procedure or received a diagnosis of a life-threatening condition.

The data came from the National Inpatient Sample compiled by the Healthcare Cost and Utilization Project, part of the federal Agency for Healthcare Research and Quality.

Admon and her colleagues, including senior author Vanessa Dalton, M.D., MPH, note that this data source allowed them to look at severe maternal morbidity across racial and ethnic groups — including American Indians and Alaskan Natives, for whom little national data have been available.

When calculating rates of severe maternal morbidity, the researchers adjusted for factors such as age, income, insurance source and rural or urban status that have already been shown to play a role in birth outcomes. They were not able to adjust for maternal obesity, another known health risk for birthing mothers.

National scope

In all, the researchers looked at data from more than 2.5 million birth hospitalizations across a four-year period — a representative sample of nearly 13.5 million births that happened in the country from 2012 to 2015.

SEE ALSO: Increasing Rates of Chronic Conditions Putting More Moms, Babies at Risk

This allowed them to calculate rates of severe maternal morbidity across women of different backgrounds and health statuses. For instance, they found that 231 of every 10,000 births among non-Hispanic black women led to one of the severe problems, compared with 139 of every 10,000 births among non-Hispanic white women.

If the rates were extended to the entire population of women who had babies in the U.S. from 2012 to 2015, more than 218,000 of them would have suffered a life-threatening problem.

Chronic conditions affect births

In addition to blood transfusions, researchers compiled rates of blood-clotting disorders, heart failure, hysterectomy during or after delivery, acute lung problems, kidney failure, eclampsia (seizures caused by high blood pressure), shock and sepsis.

Again, disparities between whites and blacks of non-Hispanic backgrounds emerged: 50.5 black mothers per 10,000 needed a lifesaving treatment other than a transfusion, compared with 40.9 white mothers per 10,000.

The researchers also focused on the prevalence of chronic health conditions that previous research has shown can increase the risk of a tricky birth. These included diabetes, chronic high blood pressure, chronic lung disease such as asthma, chronic heart or kidney disease, lupus, pulmonary hypertension, HIV/AIDS, depression and substance use disorders.

Non-Hispanic white women had higher rates overall of depression and substance use disorders compared with women from any other group. Even so, the risk that a white woman with depression or substance issues would have a severe problem during birth was significantly lower than the risk experienced by a woman of color who had depression or substance issues.

Next steps

The research sheds further light on women of color as a high-risk population for problems that could occur during delivery and immediately afterward.

Targeting health care efforts in facilities that care for higher percentages of women of color should be a priority, Admon adds.

SEE ALSO: Study: Medicaid Improves Access to Family Planning

She also hopes to do more research on the longer-term health of newly delivered mothers, beyond the initial birth hospitalization, to understand patterns of health emergencies or "near misses" in the first year after birth.

"Taking care of pregnant women, it's really heartbreaking to see women entering pregnancy or delivery in a state of health that you know could have been optimized, such as high A1c levels in diabetes, uncontrolled asthma or untreated substance use disorders," Admon says.

"Part of that has to do with underlying disparities in access to care prior to pregnancy, which is also necessary to address in order to ultimately reduce severe maternal morbidity and mortality in the United States."

The research was conducted while Admon was a fellow in the National Clinician Scholars Program at IHPI; she is now an assistant professor in U-M's department of obstetrics and gynecology, where Dalton is a professor.