The contribution of maternal stress to preterm birth: issues and considerations

Abstract

Preterm birth represents the most significant problem in maternal-child health, with maternal stress identified as a variable of interest. The effects of maternal stress on risk of preterm birth may vary as a function of context. This article focuses on select key issues and questions highlighting the need to develop a better understanding of which particular subgroups of pregnant women may be especially vulnerable to the potentially detrimental effects of maternal stress, and under what circumstances and at which stages of gestation. Issues related to the characterization and assessment of maternal stress and candidate biologic mechanisms are addressed.

FIGURE 1. MATERNAL PHYSIOLOGY AND FETAL DEVELOPMENT: A CASE OF RECIPROCAL DETERMINISM

External conditions during pregnancy that are appraised by the maternal brain as stressful may result in stress-related alterations in maternal physiology that, in turn, may influence fetal development and birth outcomes. However, the state of pregnancy itself produces progressive changes in maternal physiology that have been shown to alter maternal peripheral (physiological) responses to a variety of physical, psychological and pharmacological challenges, and also maternal central (psychological) responses to a social stressor. These pregnancy-related changes in maternal physiology (that alter maternal psychological and physiological responses to exogenous stressors) originate from the fetal-placental compartment. Hence, the fetus, the object of maternal stress-related physiological perturbations, also is the initiator of alterations in maternal physiology that progressively dampen maternal responses to exogenous (and likely endogenous) challenges – a case of reciprocal determinism.

FIGURE 2. CONTRIBUTION OF MATERNAL STRESS AND STRESS BIOLOGY TO PRETERM BIRTH: A MATTER OF CONTEXT

The is no one-to-one correspondence between psychosocial stress and a stress-sensitive biology; the nature, magnitude and duration of the effects of maternal psychosocial stress during pregnancy on any given stress-sensitive biological system are likely altered by the context of other conditions/stressors such as those related to nutrition, infection and hypoxia. Similarly, the nature, magnitude and duration of the effects of a given stress-sensitive biological system in pregnancy on maternal and fetal target systems involved in parturition are likely altered by the secondary perturbations in other closely-related biological systems and their feedback effects on the primary biological system under consideration.

FIGURE 3. MATERNAL-FETAL GENE-ENVIRONMENT INTERACTIONS IN HUMAN PARTURITION

Combinations of genes (epistasis), rather than single genes or single gene variants, likely produce effects on complex health and disease risk outcomes. For birth outcomes such as preterm birth, combinations of genes of the mother as well as the fetus need to be considered (maternal-fetal genetic interactions). The effects of certain maternal-fetal genetic combinations may vary as a function of environmental context (e.g., maternal stress level; gene-environment interactions).