Every baby is born with an instinct to suck. This is what makes a baby taking his feed. The sucking instinct even though reduced by the time the baby reaches three to four months of age. Thumb-sucking, on the other hand, developed more as a mechanism seeking the comfort of the baby.
Thumb-sucking through two to four years of age is not much worried. Most children will stop the habit when they have found more other exciting activities to do with their hands. Some children, however, continue to suck their fingers far beyond the age of 6 years. This is where the problem starts. You can also visit Amazon Canada website to find more about thumb sucking precaution.
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At this age, it has become a habit strengthened and does not easily give up. On the other hand, it leads to a lot of facial deformities while the permanent teeth erupt.
The child may have an open bite where there is a large gap visible between the upper and lower front teeth. It is very unsightly and difficult to fix even with orthodontic treatment.
Thumb or finger-sucking is sometimes seen to develop as early as 15 weeks. In the womb, the fetus is developing have their hands very close to their face and it's not much harder to find their thumbs or fingers.
Once the baby is born, though, it cannot coordinate enough limbs to bring their fingers in their mouths and often generate a lot of face scratching.