Thumb sucking
Lots of babies suck their thumb or fingers. It is part of the normal reflex infants have to root for food. As a survival technique, the sucking urge is strongest in the first three months of life. After the age of six months or so, it has more of a calming influence and helps relieve stress. If your little one sucks his thumb or fingers, especially when he’s tired, don’t get upset – it’s normal.
I think thumb sucking is so cute. My boys never sucked their thumbs but they loved the pacifier. Especially like you said, in the early months. Both thumb sucking and pacifiers can have negative impact on teeth. This great resource called the Mom’s Guide (http://www.1dental.com/moms-guide/) suggests it’s good to have your dentist take a look at your kid’s mouth around 1 years old, especially if they suck their thumb. The Mom’s Guide has other practical helps too for newborns and every stage through the teen years. Hope its a help to you too.