The role of allostatic load in adverse pregnancy outcomes: a multisystem, developmental perspective.

Allostatic load provides a valuable framework for examining how cumulative stress impacts multiple physiological systems simultaneously, making it a powerful tool for understanding the mechanisms through which stress contributes to adverse pregnancy outcomes. This multisystem perspective is especially important during pregnancy, a period characterized by heightened vulnerability to stress and significant physiological changes that can themselves contribute to allostatic load. Although the impact of allostatic load during pregnancy is well documented, the mechanisms and moderators involved by trimester remain unclear, particularly given wide variation in social, cultural, and structural determinants of maternal health worldwide. In this review, we discuss the progress that has been made over the past two decades in studying prenatal allostatic load and describe the clinical implications of this by highlighting sensitive periods of interest throughout gestation. Despite these advances, key questions remain regarding the intergenerational transmission of risk, the specificity of findings to the pregnancy period, and the role of factors that often accompany elevated allostatic load, such as poor sleep, limited social support, systemic inequities, and comorbid mental or physical health conditions, which may manifest differently across global contexts. Most existing studies have been conducted in high-income settings, yet the burden of adverse pregnancy outcomes is greatest in low- and middle-income countries, where structural, environmental, and social stressors are pervasive. Expanding this framework to include diverse global contexts is essential for understanding how social inequities and chronic stressors shape maternal physiology worldwide. We discuss these issues and offer directions for future research, including the goal of developing a standardized metric for measuring allostatic load - one that we believe will advance the field's understanding of how prenatal allostatic load markers by trimester relate to maternal and infant outcomes.