This seems counterintuitive, but turns out that as infant mortality is reduced, population sizes also decrease, because parents don't need to anticipate that their babies are going to die.
Cela semble contre-intuitif mais on a constaté que la diminution de la mortalité infantile entraînait une diminution de la population, car les parents n'avaient plus besoin d'anticiper la mort possible de leurs enfants.