Cause 1: Due to the cleft lip and palate of the child, the oral and nasal cavities are connected, and a complete closed structure cannot be formed in the mouth to produce the negative pressure required for effective sucking.
Cause 2: Due to the change in the distribution and attachment of the muscles of the lip and palate, the development and tension of the muscles are insufficient, causing the tongue to retract; at the same time, the tongue is overdeveloped and the tongue is not raised to effectively wrap the pacifier during sucking.
Cause 3, due to the shortening or inability to lift the soft palate to the imperfect function of the soft palate and affect sucking and swallowing.