There is no harm in using a pacifier while sleeping, but you need to make sure to take it out when the baby is sound asleep. The reason most parents use it is that the baby kind of gets comfortable while sleeping. However, this practice can also lower the risk of Sudden Infant Death Syndrome (SIDS). There is also another advantage of using pacifiers. Newborn babies come with a natural tendency to suck, which is why they tend to cry for bottles and breastfeed most of their time, which in turn disturbs their feeding time. If you use pacifiers, especially during sleep time, the babies use their energy to suck on these pacifiers and cry only when they are truly hungry.