My few weeks old baby hicupps almost every time after burping him and this seems to be the normal thing for babies. I'm surprised the exact cause has been poorly researched but I learned it has something to do with roughage content of food during digestion. Thanks for educating us. However, I've got a bit of reservation with the image that you used. It seems to be copyrighted. Perhaps you should replace it with image from free sources such as pixabay, peel, pixnio, Wikimedia commons, etc.