Incidence-based measures of birth, growth restriction, and death can free perinatal epidemiology from erroneous concepts of risk

Abstract

Background Traditional perinatal epidemiology appears to embrace fallacious concepts of risk. The use of incorrect denominators for perinatal rates is commonplace both for straightforward indices such as the gestational age–specific labor induction rate and also for the more conceptually challenging indices such as the gestational age–specific neonatal mortality rate. As a consequence, perinatology is beset by several conondrums including the paradox of intersecting perinatal mortality curves. Proposition These traditions are ideally replaced by alternative concepts that may be derived a priori and measured using indices such as presented here: the incidence of birth (i.e., the gestational age–specific birth rate), the incidence of growth restriction (i.e., the gestational age–specific growth-restriction rate) and the incidence of death (i.e., the age–specific mortality rate). Results The incidence of birth, growth restriction, and death quantify the core phenomena in perinatology and reveal congruent and coherent patterns of occurrence. Conclusions These new indices can free perinatal epidemiology from erroneous concepts of risk and resolve the paradoxal phenomena that plague the perinatal domain. They also permit the development of a theoretical framework for obstetric intervention, which in recent years has been based exclusively on empirical evidence.