The fetal origins hypothesis, developed by David Barker,1 proposes that when nutritional intake of a fetus is limited, the body's physiology and metabolism are changed fundamentally, and some of the consequences of these changes become apparent much later in life. Health insults in utero may lead to greater physiological deterioration of metabolic and immune systems. Early-life health may influence a broad range of subsequent disease risks over the life cycle. Over the past 2 decades, a voluminous empirical literature has documented associations between early-life health outcomes—most often, but not exclusively, low birth weight—and adult mortality and disease onset.1–5 The fetal origins hypothesis provides an explanation of why there may be important interactions between parental health status and parental economic status in their children's subsequent risk of onset of disease in adulthood.