The transition from the baby boom to the baby bust has never been studied with a particular focus on the increase in the relative costs of children. This article uses this explanation and applies it to Lausanne and Fribourg, two Swiss cities characterized by different institutional contexts and by strikingly divergent trends in terms of fertility. This article conjectures that new rights for children and models of parenthood that appeared during the 1960s increased the cost of child rearing and are key explanations for the transition from the baby boom to the baby bust.