PRB

Racism-related stress may help explain why Black women in the United States are over 50% more likely to deliver a premature baby than white women.

Just over 14% of Black women have premature births compared with 9% of white women.¹These stark racial disparities have been documented for more than a century, reports Catherine Cubbin of the University of Texas at Austin, who calls them “alarming.”

Characteristics like a mother’s health, education, and income account for less than half of the disparity, and researchers have long sought answers to further explain the gap.² Growing evidence suggests that racism-related stress may contribute to premature births.³

Premature or preterm birth (before 37 weeks of gestation) is one of the most common causes of infant mortality in the United States.⁴

“Many people think that small and premature babies will by and large ‘catch up’ in weight and live long and healthy lives—and fortunately, many do,” Cubbin says. “What may come as a surprise though is that premature birth increases both the risk of death and multiple, serious disabilities for those babies. It also raises the risk of chronic diseases and early death when those babies become adults.”

Racism-Related Stress Could Be Key to Explaining Black/White Gap in Premature Births

Researchers have been unable to fully explain the racial gap in premature births.

A large body of research shows that known risk factors for premature births—such as smoking during pregnancy—only explain a portion of this racial disparity, according to Cubbin. For example, a new study shows that a non-smoking Black woman faces the same odds of delivering prematurely as a white woman who smokes up to nine cigarettes per day before and during pregnancy.⁵

Babies born to women with more socioeconomic resources—more education, income, and wealth—tend to fare better, research shows. But the gap between Black and white women exists at all socioeconomic levels and may even be wider among women with college degrees, Cubbin points out.⁶

The growing evidence that racism-related stress contributes to these inequities in premature birth accounts for some of the dynamics that earlier studies couldn’t unravel.

Stressful experiences that women face throughout their lives and across generations can have a powerful impact on the body, says Cubbin. “The stress can be related to interpersonal interactions like feeling socially isolated, getting passed over for a promotion, or being called racist labels, and to institutional discrimination, such as living in unhealthy neighborhoods or receiving inadequate medical care.”

Chronic stress is a risk factor for premature and low-birthweight births, she explains. Stress affects the body by raising blood pressure, increasing stress hormones, triggering inflammation, and dampening the immune system in ways that affect a growing fetus, restricting growth and/or triggering premature labor, according to Cubbin.

New studies supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) are using innovative approaches to probe the racial disparity in premature births to better identify the root causes and address them.

Twitter May Offer a Barometer of Local Racism and Stress

Experiences of racism are hard to measure, but one research team has come up with a novel approach. They are using Twitter to examine state-level sentiment toward racial and ethnic minorities and compare it with patterns of premature births.⁷

They found that a higher level of negative sentiment toward Black people by Twitter users in a U.S. state was related to higher rates of premature and low-birthweight births in that state.

The study was conducted by an eight-member team including Thu X. Nguyen of the University of California, San Francisco and Quynh C. Nguyen of the University of Maryland. It was based on more than 1.2 million tweets containing at least one word pertaining to a racial or ethnic minority merged with data on all 2015 U.S. births (4 million). Negative comments included complaints, insults, or racial slurs, while positive sentiments expressed cultural pride or denied racial stereotypes.

The researchers divided states into categories of low, medium, and high on both positive and negative sentiment. All mothers living in states with the lowest levels of positive sentiment toward Black people were 16% more likely to have a premature birth compared to mothers living in the states with the highest level.

The premature birth patterns they observed among minority subgroups were the same as those found for the full population. This similarity suggests that social environments with greater levels of hostility toward minority groups may have adverse effects for all.

Efforts to promote a more accepting and inclusive social environment may reduce premature and low-weight birth rates among all groups, the researchers suggest. An updated analysis using 2015 to 2017 birth data revealed similar findings.⁸

A Mother’s Education, Health, Other Characteristics Contribute to Racial Disparities in Premature Births

More than one-third (38%) of the Black-white disparity in premature births can be explained by mothers’ socioeconomic characteristics, such as her education level, aspects of her health, and where she lives, a new analysis shows.⁹

“Premature birth is influenced by multiple factors that we are still trying to understand,” notes Marie Thoma of the University of Maryland. “The factors we identified could still be rooted in racism, if you think about structural barriers that reduce a Black woman’s access to education and health care.”

Using advanced statistical methods, Thoma and a team of researchers quantified the contribution of a variety of factors to the racial gap in premature births using data from more than 2 million 2016 U.S. birth certificates.

Their results showed that the largest contributors to these disparities were:

• Mother’s education, which may be related to her income, health care, health insurance, access to health information, and her health habits. Her education level may also influence the physical demands of her job, her cognitive skills, and sense of control of her life.
• Mother’s marital status and whether the child’s father was listed on the birth certificate, which may reflect paternal involvement and financial support during pregnancy.
• Her source of payment for delivery, particularly Medicaid, which may reflect her ability to navigate the health care system and her access to ongoing care.
• Chronic hypertension (high blood pressure), not hypertension that developed during pregnancy (preeclampsia).

“Prenatal care did not contribute that much to explaining the disparity, which didn’t surprise us,” says Thoma. “Birth certificate data is not able to measure the quality of a woman’s prenatal care or how satisfied she was with her care, which may be a better measure of potential bias in health care delivery.”

To reduce the racial gap in premature birth, the researchers suggest that policymakers consider public health programs designed to expand health care access and enhance social support for pregnant Black women—such as prenatal care groups based in local clinics. They also recommend improving primary health care for Black women before conception, specifically targeting hypertension.

Programs that can address preeclampsia and hypertension could reduce some of the disparity in the short term before other important structural changes can occur that address the root causes of these inequalities, Thoma points out.

Racial and Ethnic Composition of Mothers’ Neighborhoods a Factor in Premature Birth Risk

The racial composition of a mother’s neighborhood also appears to shape her risk of premature birth, a new study by Cubbin, Yeonwoo Kim formerly of the University of Michigan, Shetal Vohra-Gupta of the University of Texas at Austin, and Claire Margerison of Michigan State University finds.¹⁰

The researchers focused on all single babies born to non-Hispanic Black and white women in Texas between 2009 and 2011 (more than 477,000). They linked these birth certificate data with data on neighborhood racial and ethnic composition over 20 years rather than at just one point in time. They examined and classified the proportion of Latino, non-Hispanic Black, and non-Hispanic white residents in each neighborhood in 1990, 2000, and 2010, and any change in the population share held by each racial and ethnic group between 1990 and 2000 and between 2000 and 2010. Their analysis accounted for differences in parents’ education, marital status, prenatal care, and neighborhood poverty, among other factors.

Key findings:

• No matter the racial and ethnic composition of their neighborhood, Black women have higher odds of having a premature birth than white women.
• Overall, both Black and white women are at higher odds of a premature birth if they live in a neighborhood with a persistently high concentration of Black residents.
• White women have lower odds of giving birth prematurely if they live in a neighborhood with a persistently high concentration of white residents.
• Black/white disparities are highest in neighborhoods with high ongoing concentrations of white residents (59% higher) and lowest in neighborhoods with persistently low concentrations of white residents (34% higher).

“If you have a white woman and a Black woman and all other things are equal [age, marital status, prenatal care, her education level and that of her partner, and neighborhood poverty level], the Black woman faces a higher risk of having a premature birth,” Cubbin explains.

In predominantly Black neighborhoods, both Black and white women may have limited access to health care services, lack educational and employment opportunities, and feel less safe than women living in other neighborhoods, Cubbin suggests.

In an earlier study, the researchers showed that neighborhood poverty and inequality was related to premature births but did not explain Black/white differences, suggesting that all mothers are affected by high-poverty neighborhoods and high levels of income inequality in a harmful way. But, in fact, Black women are impacted more severely.¹¹

The researchers argue that racially inclusive policies can improve the health of mothers and prevent premature birth among Black women in predominantly non-white neighborhoods by addressing key factors shaping health such as limited opportunities for adequate and affordable housing, access to health care, high-quality minority-focused health resources, sustainable income, and quality education.

This article was produced under a grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). The work of researchers from the following NICHD-funded Population Dynamics Research Centers was highlighted: University of Texas at Austin (5P2CHD042849-18), University of Maryland (5P2CHD041041-18), and University of Michigan (5P2CHD041028-18).