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In February 2009, Samantha Pierce became pregnant with twins. It was a time when things were going really well in her life.

She and her husband had recently gotten married. They had good jobs.

"I was a kick-ass community organizer," says Pierce, who is African-American and lives in Cleveland. She worked for a nonprofit that fought against predatory lending. The organization was growing, and Pierce had been promoted to management.

It felt like a good time to get pregnant. "I went to get my birth control taken out and showed up two weeks later, like 'Hey, We're pregnant!' " she says, laughing.

Pierce thought she was a poster child for a good pregnancy. She already had one son from a previous marriage, and that pregnancy was healthy and normal. She had a college degree, which is known to improve women's chances of having a healthy pregnancy. She was getting regular checkups and taking her prenatal vitamins.

Everything went smoothly until one day in her second trimester she discovered she was leaking fluid. After a week in the hospital, still leaking, her water broke and she gave birth to her sons. "They lived for about five minutes, each of them," she says. "But they couldn't breathe. They didn't have lungs. We got to hold them, talk to them. I could see them breathing. I could also see them stop breathing, you know."

Pierce was devastated. For months, she couldn't bear to look at herself in the mirror, especially her stomach. She felt as if her womb was a cemetery — "a walking tomb," she says. "It was just walking evidence of loss, of failure, of not being able to hold kids in. I couldn't even do the one thing I was put on this planet for, which was bear children."

A chilling statistic

What Samantha Pierce didn't know then was that her twins had become part of a chilling statistic. "Black babies in the United States die at just over two times the rate of white babies in the first year of their life," says Arthur James, an OB-GYN at Wexner Medical Center at Ohio State University in Columbus. According to the most recent data from the U.S. Centers for Disease Control and Prevention, for every 1,000 live births, 4.8 white infants die in the first year of life. For black babies, that number is 11.7.

The majority of those black infants that die are born premature, says James, because black mothers like Pierce have a higher risk of going into early labor.

Scientists and doctors have spent decades trying to understand what makes African-American women so vulnerable to losing their babies. Now, there is growing consensus that racial discrimination experienced by black mothers during their lifetime makes them less likely to carry their babies to full term.

James, 65, has seen far too many black babies who didn't survive.

It just doesn't seem right, says James, who is also African-American. "You ask yourself the question: What is it about being black that places us at an increased risk for that kind of experience?"

A decades-long quest

Richard David, a neonatologist at the University of Illinois of Chicago, has been studying this for decades. When he first began looking into the problem in the 1980s, he says scientists thought the two main culprits were poverty and lack of education.

"We knew African-American women were more likely to be poor," says David. "We knew that fewer of them had completed their education by the time they were bearing children."

But David, who at the time was at the Cook County Hospital in Chicago, and his colleague James Collins at Northwestern University Medical School found that even educated, middle-class African-American women were at a higher risk of having smaller, premature babies with a lower chance of survival.

For example, David says, black and white teenage mothers growing up in poor neighborhoods both have a higher risk of having smaller, premature babies. "They both have something like a 13 percent chance of having a low birth weight baby," he says.

But in higher-income neighborhoods where women are likely to be slightly older and more educated, "among white women, the risk of low birth weight drops dramatically to about half of that, whereas for African-American women, it only drops a little bit."

In fact, today, a college-educated black woman like Samantha Pierce is more likely to give birth prematurely than a white woman with a high school degree.

"That's exactly the kind of case that makes us ask the question: What else is there?" says David. "What are we missing?"

Some people suggested that the root cause may be genetics. But if genes are at play, then women from Africa would also have the same risks. So, David and his colleague, Collins, looked at the babies of immigrant women from West Africa. But as they reported in their 1997 study in The New England Journal of Medicine, those babies were more like white babies — they were bigger and more likely to be full term. So, it clearly isn't genetics, says David.

Then, many years later, David and Collins noticed something startling. The grandchildren of African immigrant women were born smaller than their mothers had been at birth. In other words, the grandchildren were more likely to be premature, like African-American babies.

This was also true of the grandchildren of black women who had emigrated from the Caribbean.

Meanwhile, the grandchildren of white European immigrant women were bigger than their mothers when they were born. David and Collins published their results in 2002 in the American Journal of Epidemiology.

"So, there was something about growing up black in the United States and then bearing a child that was associated with lower birth weight," says David.

Growing up black and female in America

What is different about growing up black in America is discrimination, says David. "It's hard to find any aspect of life that's not impacted by racial discrimination," he says. "Whether you're talking about applying for a job, or purchasing a new car, finding housing, getting education ... even given equal education, earning the same amount of money, that doesn't happen. If you're black, you tend to get less pay."

As a recent poll by NPR, the Robert Wood Johnson Foundation and the Harvard T.H. Chan School of Public Health found, 92 percent of African-Americans believe that discrimination against African-Americans exists in America today. Higher education and income did not necessarily mean people experienced lessdiscrimination, the poll found.

In 2004, David and Collins published a study in the American Journal of Public Health in which they reported the connection between a mother's experience of racism and preterm birth. They asked women about their housing, income, health habits and discrimination. "It turned out that as a predictor of a very low birth weight outcome, these racial discrimination questions were more powerful than asking a woman whether or not she smoked cigarettes," David says.

Other studies have shown the same results.

Samantha Pierce didn't know this when she was pregnant back in 2009. But she did know discrimination. She was 7 or 8 years old the first time someone called her the N-word. She was with her mother, visiting Murray Hill, Cleveland's Italian neighborhood.

"We were just driving through," she says. "We were driving, literally with our windows down, and we were called niggers, just going up the hill."

The memory still makes her angry. "It does not matter that my mother owned her own home," says Pierce. "It does not matter that we owned that car, because we did! It did not matter that I went to private school, because I did! When I was riding up Murray Hill, I was a nigger, and so was my mother."

It wasn't the only time she was made to feel inferior for being black. She felt it at school, too.

Pierce remembers her mother warning her early on in her childhood that she would have to "work twice as hard to get half as much" as her white counterparts, she says.

She says her mother's words ring true even today at work.

Then there is the everyday racism, says Pierce, like being shadowed at stores by the staff, even when she is with a white friend. Pierce says her white friends don't even notice. These kinds of things happen every day, she says.

Black women are often the primary breadwinner and caregiver, Arthur James from Ohio State notes. That is partly because of the higher incarceration rate and unemployment rate among black men, he says. "That's added to the burden of black women." That burden and the stress from discrimination, it all adds up, he says.

Stress and labor

When we are stressed, our bodies produce stress hormones. When the source of stress goes away, so do the stress hormones. It's a normal, healthy process. But when someone is stressed out all the time, their bodies have perpetually high levels of stress hormones.

Stress hormones are also naturally high during normal, full-term labor. But if a woman goes into a pregnancy with already high levels of stress hormones, she is more likely to deliver prematurely, says James.

"We think that higher levels of stress hormones increase the incidence of pre-term labor," he says.

When Samantha Pierce first learned about this, a few years after her twins died, it was as if a light bulb went off. "Stress leads to labor. And African-American women live a more stressful life," she says. "And so we hit preterm birth at an alarming rate."

Pierce went on to get pregnant again. This time, too, she had twins. She was placed on bed rest, but the pregnancy went smoothly. Her twins — a boy and a girl — are now 7 years old and healthy.

These days, Pierce is on a mission to fight back against all the stress for her generation of black women and also her daughter's. And she uses exercise as a weapon. She works out regularly at a gym in Cleveland with other women. And she is now a certified personal trainer. Her clients are mostly African-American women.

Exercise isn't just about getting fit, she says. It can also provide social support, which many black women say they lack.

"We really are hard on ourselves," says Pierce. "And so we really need other women, especially other black women to say, 'I see you. You're doing fine. Keep going.' "

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