How do prenatal and postnatal circumstances interact in shaping health? An interdisciplinary approach using quasi-experiments

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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. Our research combines medicine/epidemiology with an econometric-statistical approach.The prenatal phase is known to have long-run implications on health. 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 adapt physiologically not only in response to adverse circumstances. I.e. prenatally, 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. In this sense, such Predictive Adaptive Responses (PARs) allow a species to quickly adapt to variations in circumstances it may be confronted with. If the environment encountered during gestation however differs strongly from the postnatal environment encountered by the offspring, PARs 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 due to the impossibility to do experiments on humans: researchers solved this by utilizing clearly demarcated, relatively short – clearly adverse – historical periods, such as famines. Such circumstances were unlikely to be followed by similar circumstances later in life, so that 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 is an interdisciplinary cooperation between an applied econometrician, who is specialized in the application of natural/quasi experiments in the health domain, and an epidemiologist/medical researcher, who have already been working together successfully. We 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 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 human health, and to accordingly further refine this framework.