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 baby one right away. I am breastfeeding my 6 month old son, but he never take a pacifier, so he always sucked on me. :( But just try different brands. Maybe even try some toys that your baby can suck on. If your baby does end up taking a pacifier, you will want to discontinue use at 3 to 4 months. Helpful.