Stress and violence during the nine months in utero has been widely shown to have important effects on child development. To date this research has largely focused on extreme and relatively rare events. This column uses data from Brazil to explore how exposure to day-to-day violence can affect birth weight. The birth weight of newborns whose mothers are exposed to a homicide during their first trimester is significantly lower. This effect is smaller for mothers who live in more violent neighbourhoods, consistent with the interpretation that violence is more stressful when it is rare.