Each year, a half million babies in the United States are born too early, causing complications that make prematurity the number one cause of infant death in the country. African American women are almost two times more likely to deliver a preterm baby than women of other races, a disparity that is not been fully explained by socioeconomic status, access to healthcare, or health behaviors.

Now, by exploring the complex associations between race, stress, inflammation and pregnancy, researchers at The Ohio State University Wexner Medical Center have uncovered biological and behavioral clues that could help lead to new interventions and ideas for reducing premature births.

"Psychological stress, including the stress of racial discrimination, has been associated with risk for preterm birth in many studies. However, we know little about the biological mechanisms that may contribute to this increased risk," said lead author Lisa Christian, PhD, an assistant professor of Psychiatry and the Institute for Behavioral Medicine Research (IBMR) at Ohio State. "Prior studies suggest that, during healthy pregnancy, cardiovascular and neuroendocrine responses to stress are dampened. This study examined whether this dampening also occurs in relation to stress-induced inflammation. And, if so, do African American women show such dampening to the same extent as white women."

Race, acute stress trigger exaggerated inflammatory response

In a study of white and African American women, both pregnant and non-pregnant, Christian's team found that African American women showed stronger inflammatory response to acute psychological stress.

Published in Psychosomatic Medicine, and supported by a pilot grant from Ohio State's Center for Clinical and Translational Science (CCTS) and an R21 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) the study matched a group of 78 white and African American women by income, age and pregnancy status.

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To trigger a stress response, researchers had the women participate in a fictional job interview with two female interviewers, one white, one African American. Participants had blood and saliva taken before the interview and at intervals after the interview to measure levels of the proinflammatory cytokine interleukin (IL)-6 and cortisol -- two primary "stress chemicals" associated with inflammation.

Study participants were also given a series of psychosocial tests to measure their exposure to perceived discrimination, stress, anxiety, depression, and level of family or community support, as well as health behavior questions about sleep and exercise.

"We found that, in response to the stressor, African American women had a 46% greater increase in IL-6 in their blood than their white counterparts," said Christian, who has been studying the impact of inflammation on pregnancy for 8 years. "We also found that, during pregnancy, white women found the stressor to be subjectively less stressful compared to non-pregnant women. However, this change in how stress was perceived was not seen in the African American women."

Christian says these results differ from previous studies which have focused on stressor exposure. "Here we show that the ultimate physical impact of stress is actually the combination of stress exposure and the biological response to that stressor. If a woman is exposed to repeated or chronic stress, it may change how her body responds to everyday stressors -- including higher inflammatory responses which are potentially detrimental."

Christian hopes that evidence of the inflammatory reactivity seen in her study gives physicians and researchers new intervention ideas that could potentially reduce the number of preterm births.

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"What if we could improve outcomes for African American women and their babies simply by taking steps to help them dial down the inflammatory response to stress? That would be a game changer. And it could affect health in women well beyond pregnancy."

Factors affecting self-rated health may differ in pregnant African-American women versus whites

In another study, also supported by the CCTS, Christian found that demographic, behavioral, and psychosocial factors may also influence how healthy pregnant women perceive themselves to be.

"While numerous studies have found a correlation between a patient's self-rated health and actual health or behaviors, there have been few studies looking at which factors influence self-rated health of pregnant women, " said Christian, "How people perceive their own health affects their motivation to make positive changes in their behaviors, such as diet or smoking."

Published in the Annals of Behavioral Medicine, the study observed that pregnant African American women were more likely than pregnant white women to rate their health as excellent, even when objective measures such as concurrent health issues, body mass index and smoking status indicated otherwise. Christian speculates that this may be due to a tendency for women to compare themselves with others in their community.

"Statistically, African-Americans have a higher incidence of chronic illnesses such as heart disease and diabetes. If women are comparing themselves to others in their community who have serious illnesses, then they may think that they are doing pretty good in comparison," said Christian. "Understanding this point of view gives clinicians opportunities to probe a little more during prenatal visits."

Christian notes that more research is needed to better understand the complex relationship between such diverse factors like inflammation, race and pregnancy, but says that her research has a very basic message about maternal mental health that applies to all women.

"Women who are very conscientious about their health behaviors, such as taking prenatal vitamins and avoiding alcohol, may not take the same time to focus on their emotional well-being," said Christian. "I would tell an expecting mother to work with her doctors to proactively address life stressors. That way she can not only enjoy her pregnancy and prepare for the new baby, but she may ultimately improve her pregnancy outcomes and help her developing baby."

Christian notes that both studies have an important limitation: birth outcomes were not included due to the fact that the preterm delivery rate was lower than the national average. She says that this was not unexpected as women with major health or substance abuse issues were excluded from the studies.