Stress and Blood Pressure During Pregnancy: Racial Differencesand Associations With BirthweightCLAYTON J. HILMERT,PHD, CHRISTINE DUNKEL SCHETTER,PHD, TYAN PARKER DOMINGUEZ,PHD, MPH, MSW,CLEOPATRA ABDOU, MA, CALVIN J. HOBEL, MD, LAURA GLYNN,PHD, AND CURT SANDMAN,PHDObjective: To extend findings that African American women report greater stress during pregnancy, have higher blood pressure(BP), and are twice as likely to have low birthweight infants relative to white women. This study examines a) racial differencesin associations between stress and BP during pregnancy, and b) the combined effects of stress and BP on infant birthweight in asample of 170 African American and white women. Methods: A prospective, longitudinal study of pregnant women was conductedin which measures of BP, stress, and other relevant variables were collected. Multiple measures of systolic and diastolic BP weretaken at each of three points during pregnancy (18 –20, 24–26, and 30 –32 weeks gestation). Results: Both systolic blood pressure(SBP) and diastolic blood pressure (DBP) were positively associated with stress in pregnant African American women and not inpregnant white women. In analyses of birthweight, there were no main effects of BP or stress. However, a significant interactiondemonstrated that, when stress was high, DBP was negatively associated with birthweight and a combination of high stress and highDBP predicted the lowest birthweight in the sample. Furthermore, African American women were twice as likely as white womento have a combination of high stress and high DBP. Conclusions: Racial differences in relationships between stress and BP, andthe interactive effect of stress and DBP on birthweight together suggest that a high stress-high BP profile may pose a risk for lowerbirthweight among African American women, in particular, and possibly for all pregnant women. Key words: pregnancy,birthweight, African American, blood pressure, stress.BP ⫽ blood pressure; DBP ⫽ diastolic blood pressure; SBP ⫽systolic blood pressure; BMI ⫽ body mass index; Ms ⫽ means.INTRODUCTIONAfrican American women are twice as likely to give birthprematurely and to have low birthweight infants com-pared with white women (1). These racial differences consti-tute some of the most dramatic health disparities in the UnitedStates. To address this issue, research has generally focusedon identifying characteristics of African American womenthat are less prevalent in a lower-risk group, such as whitewomen. Research has also examined associations betweenthese individual characteristics and birth outcomes identifyingpsychosocial and biological variables, such as high stress andincreased blood pressure (BP) responses to stress as indepen-dent risk factors contributing to racial disparities in adversebirth outcomes (2). However, researchers have been unable toaccount for why African American women are at such highrisk for adverse pregnancy outcomes (3,4). Therefore, we takea different approach and consider the combined effects ofbiological and psychosocial risk factors on birthweight toprovide new insights into the persistent racial disparities inbirth outcomes.Blood Pressure: Biological Risk FactorIn the general population, African Americans have agreater incidence of clinical hypertension than whites (5). Ithas been estimated that twice as many African Americanwomen as white women enter pregnancy with preexistinghypertension (6). Hypertension (systolic BP (SBP) ⱖ140mm Hg; diastolic BP (DBP) ⱖ90 mm Hg) during pregnancyis a serious risk factor for fetal growth restriction and pretermdelivery, and can be fatal to the pregnant woman or fetus ifthis condition goes untreated (7,8).Less well understood are the implications of subclinicallevels of BP. Although research suggests that variations insubclinical BP are related to cardiovascular health in nonpreg-nant African Americans (9), subclinical BP during pregnancyis understudied. There are several changes in physiology dur-ing pregnancy, including systematic adjustments in maternalblood volume and BP (10,11) that make this an important areaof independent study.Stress: A Psychosocial Risk FactorA number of theories have predicted associations betweenvarious conceptualizations of stress (e.g., stressful life events,stress appraisals) and health (12), at times suggesting distinctpathways by which different forms of stress affect health (13).As members of a racial minority group, African Americanwomen face a large range and notable combination of stres-sors (14). Research has shown that African American pregnantwomen tend to report more stressful life events (4) and greaterpsychosocial distress from life events compared with otherracial groups (15).There is a significant body of evidence linking psychoso-cial stress (stressful life events, stress responses, anxiety,appraisals of stress) to a variety of birth outcomes, includinglower birthweight and shorter length of gestation (1,16,17).One approach to understanding stress and pregnancy out-comes in African Americans is the theory of allostatic load inwhich physiologic wear and tear resulting from responses tochronic and repeated acute stress may lead to dysregulation ofFrom the Department of Psychology (C.J.HILMERT.), North Dakota StateUniversity; Department of Psychology (C.D.S.), University of California, LosAngeles; School of Social Work (T.P.), University of Southern California;Department of Psychology (C.A.), University of California, Los Angeles;Department of Obstetrics and Gynecology (C.J.HOBEL.), Cedars-Sinai Med-ical Center; Department of Psychiatry and Human Behavior (L.G., C.S.),University of California, Irvine, Irvine, California.Address correspondence and reprint requests to Clayton J. Hilmert, De-partment of Psychology, North Dakota State University, Fargo, ND 58105-5075. E-mail: [email protected] for publication August 13, 2006; revision received August 15,2007.This research was supported by Grant R01-HD28413 and T32-MH15750fellowships from the National Institute for Child Health and Human Devel-opment (C.J.H., C.A.).DOI: 10.1097/PSY.0b013e31815c6d9657Psychosomatic Medicine 70:57– 64 (2008)0033-3174/08/7001-0057Copyright © 2008 by the American Psychosomatic Societythe body’s stress response systems and contribute to negativehealth outcomes (14,18,19).A lifetime of allostatic load may cause African Americanpregnancies to be particularly susceptible to the negative con-sequences of