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).
You can give your newborn a little sip of water. The swallowing action may be enough to get the diaphragm back under control. Letting your baby suck on a pacifier could also lead to the same positive results. You may also have tried holding your breath for a few seconds to get the hiccups to stop.