Heterogeneity of Risk

Abstract Heterogeneity of risk is the core of epidemiology, and this is nowhere more evident than in reproductive studies. Most adverse reproductive outcomes vary widely in their risk within populations, with some families at low risk and others at high risk. An important dynamic in reproductive epidemiology is the way that previous pregnancy outcomes affect selective control of fertility to distribute high- or low-risk couples in misleading ways. Patterns of risk that may seem to reflect biologically based causal mechanisms can be created by heterogeneity and selection. Examples are shown for family recurrence patterns of miscarriage and perinatal mortality.