The Causal Relationship between Fertility and Infant Mortality: Prospective Analyses of a Population in Transition

Hillard S. Kaplan, University of New Mexico
Paul L. Hooper, University of New Mexico
Jonathan Stieglitz, University of New Mexico
Lisa S. McAllister, University of California, Santa Barbara

This paper examines causal processes underlying change in demographic outcomes among the Tsimane of lowland Bolivia. Using prospective data collected between 2002 and 2010, we show that the loss of an infant leads to an earlier progression to the next birth, as do prospective measures of maternal health and energy balance. The total fertility rate is about 9.0, but greater integration with the Bolivian market and educational system is associated with lower fertility rates. The data indicate tangible trade-offs between fertility and infant mortality. Infants of first-time mothers who delay reproduction show significantly improved survival rates. For parous mothers, short interbirth intervals increase the mortality risks of subsequent infants. Infant mortality is also significantly predicted by indicators of the mother's nutritional and health status. We discuss these results in light of broader secular trends in demographic rates in South America as a whole.