摘要：Objectives. We examined the impact of preconception acute and chronic stressors on offspring birth weight and racial/ethnic birth weight disparities. Methods. We included birth weights for singleton live first (n = 3512) and second (n = 1901) births to White, Mexican-origin Latina, other-origin Latina, and Black women reported at wave IV of the National Longitudinal Study of Adolescent Health (2007–2008; ages 24–32 years). We generated factor scores for preconception acute and chronic stressors from wave I (1994–1995; ages 11–19 years) or wave III (2001–2002; ages 18–26 years) for the same cohort of women. Results. Linear regression models indicated that chronic stressors, but not acute stressors, were inversely associated with birth weight for both first and second births (b = −192; 95% confidence interval = −270, −113; and b = −180; 95% confidence interval = −315, −45, respectively), and partially explained the disparities in birth weight between the minority racial/ethnic groups and Whites. Conclusions. Preconception chronic stressors contribute to restricted birth weight and to racial/ethnic birth weight disparities. Birth weight, a marker of infant health, predicts infant survival and subsequent health status. Low birth weight, defined as weight less than 2500 grams, is associated with increased risk of developing both short-term and long-term health problems. 1 The prevalence of restricted birth weight has been increasing since the 1980s in the United States, 2 and marked differences in birth weight persist by race/ethnicity. 3,4 Limitations of prenatal care and other pregnancy interventions to address the increase over time and disparities in prevalence of adverse birth outcomes 1,5 have led to a focus on preconception health, defined broadly as health before a pregnancy (although often used in public health practice to denote health during the reproductive years) and including interconception health, or health between pregnancies. 6,7 Drawing on a life course framework, 8–10 the concept of preconception health suggests that infants are affected not only by maternal exposures in the 9-month prenatal period, but also by maternal development before the pregnancy. One preconception exposure of interest is stress. Pearlin’s stress process model posits that social characteristics including those surrounding race/ethnicity in the United States lead to stress exposures that affect health, 11–13 and has been used to understand elevated risk of adverse health outcomes among minority groups. 14,15 It is worth noting that elevated stress is not inherent to persons of minority race/ethnicity, because race/ethnicity is a social construct and not a biological one. Rather, stress results from historical and societal constraints leading to differential life chances across groups. 16 In studies of its health consequences, stress was defined most frequently as exposure to an inventory of life events within a specified period of time. 17 These acute stressors, such as a death in the family or exposure to a crime, are relatively brief in duration but may have continued ramifications. 17,18 Consistent with a life course perspective, more recent studies examined chronic stressors as a risk factor for health outcomes. 18,19 These stressful life conditions, including individual and neighborhood socioeconomic disadvantage, recur or accumulate throughout a respondent’s life. However, measurement of chronic stressors is less standardized across studies than that of acute stressors; validated scales of acute events 19 but not chronic conditions have been developed. Physiologic mechanisms have been hypothesized to link maternal stress to maternal and infant health. 20–22 For example, cumulative stress exposure may result in accelerated aging, or “weathering,” wearing down the body’s adaptive systems. 21,22 Weathering in particular was proposed as a source of racial/ethnic disparities in perinatal health, such that the higher stress experienced by African American women causes their reproductive functioning to deteriorate more rapidly than that of White women. 22 Other possible pathways through which stress can lead to birth outcome disparities include infection, 23 nutrition, 19 and pregnancy complications. 24 The majority of studies assessing the effects on birth outcomes of stress and related factors have relied on prenatal measurement with mixed results. 19,25,26 A smaller number of studies have examined effects of acute stressors or specific chronic stressors in the reproductive period. 27–30 Although several of these analyses suggested associations, this work included limitations such as small sample sizes, 27 European cohorts not generalizable to the United States, 29 or retrospectively reported preconception measures. 30 Furthermore, none included both acute and chronic stressors or compared racial/ethnic differences for groups besides non-Hispanic Black and non-Hispanic White. To address these gaps in the literature, the objective of this study was to examine the impact of maternal preconception acute stressors (or stressful life events) and preconception chronic stressors (or stressful life conditions) on offspring birth weight and racial/ethnic birth weight disparities. Our hypotheses were as follows: (1) acute and chronic stressors will be inversely associated with birth weight, (2) the distributions of birth weight and stress will vary by maternal race/ethnicity, and (3) stress will partially explain racial/ethnic differences in birth weight where such differences exist. Our conceptual model is shown in Figure 1 . Open in a separate window FIGURE 1— Conceptual model depicting hypothesized relationships among maternal race/ethnicity, preconception stress, and offspring birth weight: National Longitudinal Study of Adolescent Health, United States, 1994–2008.
