NJ Baby Blog:

All babies (and all humans!) experience gas, the normal byproduct of digestion.  For babies, gas frequently becomes trapped in baby’s tummy creating a painful sensation because in addition to digestion, babies are also taking in and swallowing air through their normal activities like crying, sucking a pacifier or nursing or drinking a bottle.  This is normal and common, but there are ways to try to minimize gas pains before they start, and treat them after they begin: