A newborn’s thumb may be a sign of normal hypertonia or cerebral palsy, which needs to be evaluated by a doctor. 1. Normal hypertonia: Due to the underdevelopment of the brain and nervous system, newborns may have hypertonia, which may be manifested as an inward-facing thumb. If the child does not have a history of oxygen deprivation, and has a normal spirit, appetite, and sleep, this kind of inward thumb snap may be normal. 2. Cerebral palsy: If the newborn’s thumb is obvious, and there is a history of hypoxia and asphyxia at birth, this may be a manifestation of cerebral palsy, which will have the manifestation of generalized muscle tension increase, causing the backwardness of gross motor development, affecting the growth and development in the future, and this is an abnormal situation. If the condition persists, it is recommended to consult a doctor to find out the cause of the condition and treat it as soon as possible.