A nationwide cohort of more than 1.8 million liveborn, singleton infants gave us the opportunity to test the hypothesis that maternal overweight and obesity are associated with infant, neonatal, and postneonatal mortality. As maternal BMI is positively associated with risk of preterm delivery, we also wanted to investigate these associations stratified by preterm and term births. Finally, we wanted to study whether maternal overweight and obesity are associated with specific causes of
infant death.