According to doctors' recommendations, babies should be breastfed for the first 6 months of life. From about 2-3 months old, you may see your baby start to frequently suck his/her thumb. This may be a harmless action, but sometimes it also brings some problems that need intervention, especially when the baby sucks his/her thumb and refuses to suck. So what should you do when your 3-month-old baby sucks his/her thumb, when should you intervene, and how should you handle a baby who sucks his/her thumb but refuses to suck?