There are strong reasons to expect that prenatal and postnatal circumstances interact in shaping health, but this has hardly been studied in humans. We develop a framework for studying such effects and rigorously test this in a series of studies on specific prenatal/postnatal interactions. Fetal programming theory describes how exposures to environmental circumstances during critical developmental phases set off adaptations that result in permanent changes to an organism’s physiology. Research on humans has focused on a wide range of adverse circumstances such as famines, pollution and toxic substances, stress, and non-famine nutritional deficits and showed negative long-run health effects. Animal studies demonstrate that organisms have a certain phenotypic plasticity that allows them to adapt to their environment, e.g. via epigenetic changes. This can be beneficial when prenatal circumstances serve as correct predictions for postnatal environments. However, if pre- and postnatal environments differs, such adaptations may have harmful effects. Human early-life effects studies usually focused on how adverse prenatal circumstances lead to adverse later-life health outcomes, generally ignoring potential interactions with postnatal circumstances. This may be because the natural experiments utilized, such as famines, were unlikely to be followed by similar circumstances later in life. It thus sufficed to establish that the prenatal environment caused long-run health damage, without a need to study whether it makes a difference whether pre- and postnatal circumstances match or mismatch. Our project will study prenatal/postnatal interactions using observational data by combining natural experiments that lead to quasi-random variation in prenatal circumstances with natural experiments that lead to quasi-random variation in postnatal circumstances. We include five empirical research projects, that together provide a solid test of our research framework. We will use these projects to demonstrate whether and how prenatal/postnatal interactions shape humans’ health, and to accordingly further refine this framework.
Key targets: 1. To provide high-level evidence on whether and how prenatal-postnatal interactions occur in a range of different scenarios. 2. Based on the results of these scenario studies: to refine the framework on the functioning of prenatal-postnatal interactions in humans.
PIK contribution: This is a close interdisciplinary cooperation between an applied econometrician in Mainz (Reyn van Ewijk) who is specialized in the application of natural/quasi experiments in the health domain, and an epidemiologist/medical researcher with expertise in nutrition and climate change at PIK (Sabine Gabrysch). All studies will be done jointly. Nevertheless, each study (and resulting article) will be assigned to a key responsible person. The first author for the papers from study 3 and 5 will be the doctoral researcher hired at PIK, since the Climate Change and Health team at PIK has most experience regarding nutritional interventions, as well as with infectious diseases and randomized field experiments in low-income countries. Study 3: Prenatal & postnatal exposures along the same dimension: rainfall/Ramadan and supplementary feeding programs Study 5: Prenatal & postnatal exposure along different dimensions: nutrition and malaria prevention
