Abstract

A negative association between birth spacing and infant and child mortality has been consistently identified within modern populations in developing countries. Generally speaking, children born following shorter birth intervals have been found to have higher mortality (Hobcraft, McDonald, & Rutstein, 1985; Kozuki et al., 2013; Rutstein, 2005). The reasons for this association are unclear, however. Leading hypotheses attempt to explain these differences as a result of maternal depletion, sibling competition, sibling contagion, or unobserved maternal factors that simultaneously influence fertility and infant mortality (e.g. inadequate breastfeeding practices), but none has attained overwhelming support. This study contributes to this body of research in a few important ways. First, it examines this association in a historical context, which has largely been ignored (see Pebley, Hermalin, & Knodel, 1991 for a notable exception). The data come from the Roteman Database, a longitudinal register kept for Stockholm, Sweden between 1878 and 1926. Second, and more importantly, it attempts to isolate some of the hypothesized causal mechanisms by studying variation within families using models that control for maternal fixed-effects thereby eliminating the potential for compositional differences among mothers to drive this relationship. Results suggest that the relationship between preceding interval length and mortality holds even when accounting for unobservable maternal factors. Shorter intervals had the largest impact on post-neonatal and early childhood (age 1-4) mortality, yet had rather small influence on neonatal mortality. No relationship between preceding interval length and older child (age 5-9) mortality could be identified. The importance of the sibling competition and sibling contagion hypotheses were then assessed by exploiting variation in the timing of deaths among previously born children. The results point to greater importance of sibling competition in the prenatal period, but a greater role for sibling contagion in the postnatal period.