Cold ambient temperature in utero and birth outcomes in Uppsala, Sweden, 1915 to 1929

Although the literature finds adverse birth outcomes following exposure to ambient heat waves in utero, less work focuses on infant health following cold stress. We address this gap in the literature and employ rigorous methodology to test the relation between cold ambient temperature in utero and four perinatal outcomes. We examined 14,000 births in Uppsala, Sweden (1915 to 1929), a population that—unlike most societies today—experienced sub-standard indoor-heating and fewer amenities to provide shelter from ambient cold. Results, which control for season of birth, indicate that the risk of both stillbirth and preterm delivery rises as ambient temperature over gestation falls. Exploratory analyses by sex indicate that the increased risk of preterm appears confined only to male births. Infant birth length (but not birth weight) also declines with lower temperatures. In this historical population, cold stress adversely affects fetal development. Our work holds relevance to maternal-fetal biology as well as to contemporary societies (e.g., indigenous Arctic populations) with limited resources to mitigate the adverse consequences of cold.