Early-Life Nutritional Ecologies and Perinatal Outcomes among Immigrants

Research on migrant perinatal outcomes has much focused on how and why migration protects against unhealthy low birth weights, often overlooking the emerging risk of fetal macrosomia among immigrant populations. We propose a multi-sited, life-course framework that links early-life exposure to nutritional deprivation in mothers' countries of origin to perinatal outcomes in destination. Using unconditional quantile regression on Spanish birth registry microdata linked with historical FAO nutritional series, we reveal a dual pattern: immigrant status confers protection at the lower tail of the birthweight distribution but predicts excessive growth at the upper tail. To explain this paradox, we test competitive nutritional mechanisms. We find that adjusting for historical caloric availability yields null results, ruling out simple energy-deficit hypotheses. In contrast, adjusting for the scarcity of key macronutrients—specifically Fats and proteins—attenuates the macrosomia risk by nearly 80% at the 95th percentile. This validates a qualitative nutritional mismatch mechanism: metabolic efficiency programmed by early lipid scarcity becomes maladaptive in the obesogenic destination environment. Heterogeneity analyses confirm that this mechanism is specific to populations undergoing drastic lipid transitions such as Latin Americans, highlighting the enduring biological legacy of origin-country nutritional ecologies.