Utility is an economic term for a person's overall well-being and satisfaction. Consumers play a role in the economy by maximizing utility, which means allocating their scarce resources, such as limited time or money, most efficiently. Utility maximization is different for every person.
You can start using it right away but it was suggested to us by our midwives to hold off until 6 weeks as pacifier use can mess with their breastfeeding latch (it's a different kind of sucking).
Pacifiers: Satisfying Your Baby's Needs. All babies are born with the need to suck. This is important because babies need the sucking reflex to eat and drink. Sucking for some babies also can have a soothing and calming effect. If your baby wants to suck beyond what nursing or bottle-feeding provides, a pacifier may satisfy that need.