This study estimates the causal effects of prenatal exposure to air pollution on newborn health using population-wide administrative data from Czechia covering more than 3 million births between 1994 and 2024, linked to daily measures of multiple air pollutants across the country. While a large literature documents associations between air pollution and adverse birth outcomes, establishing credible causal effects remains challenging due to residential sorting, confounding maternal characteristics, and high collinearity across pollutants. To address these challenges, we employ a sibling fixed-effects design that compares siblings born to the same mother under different levels of prenatal pollution exposure, thereby accounting for unobserved time-invariant maternal characteristics.
Our preliminary results indicate that prenatal exposure to higher levels of air pollution reduces birth weight. We find negative effects across several pollutant categories, including gaseous pollutants, particulate matter, and heavy metals. Exposure to elevated pollution levels also increases the probability of low birth weight (below 2500 g), which affects more than 5% of newborns in the sample. The strongest effects are observed for heavy metals such as nickel and lead. Additional analyses are ongoing and include alternative newborn health outcomes based on Apgar scores as well as instrumental-variable approaches exploiting exogenous variation in meteorological conditions, including wind speed, wind direction, precipitation, and surface pressure.
