Preconceptional stress and racial disparities in preterm birth: an overview

Abstract

Objective: We reviewed the evidence for three theories of how preconceptional psychosocial stress could act as a contributing determinant of excess preterm birth risk among African American women: early life developmental plasticity and epigenetic programming of adult neuroendocrine systems; blunting, weathering, or dysfunction of neuroendocrine and immune function in response to chronic stress activation through the life course; individuals' adoption of risky behaviors such as smoking as a response to stressful stimuli.

Methods: Basic science, clinical, and epidemiologic studies indexed in MEDLINE and Web of Science databases on preconceptional psychosocial stress, preterm birth and race were reviewed.

Results: Mixed evidence leans towards modest associations between preconceptional chronic stress and preterm birth (for example common odds ratios of 1.2-1.4), particularly in African American women, but it is unclear whether this association is causal or explains a substantial portion of the Black-White racial disparity in preterm birth. The stress-preterm birth association may be mediated by hypothalamic-pituitary-adrenal axis dysfunction and susceptibility to bacterial vaginosis, although these mechanisms are incompletely understood. Evidence for the role of epigenetic or early life programming as a determinant of racial disparities in preterm birth risk is more circumstantial.

Conclusions: Preconceptional stress, directly or in interaction with host genetic susceptibility or infection, remains an important hypothesized risk factor for understanding and reducing racial disparities in preterm birth. Future studies that integrate adequately sized epidemiologic samples with measures of stress, infection, and gene expression, will advance our knowledge and allow development of targeted interventions.

Figure 1

Risk for very preterm birth (<32 weeks’ gestation) by maternal age and race, USA, 2003–2006. Data source: National Center for Health Statistics. Arrows point to lowest risk point in age curve for Black (solid line) and White (dotted line) mothers. At all ages, Black mothers experience higher risk for very preterm birth than White mothers, but the nadir of risk for Black mothers is shifted to the left (younger ages) and the rate of increased age-specific risk after the nadir is steeper in Black than in White mothers.