Related to tongue tie (and its posterior hidden variant) which may cause problems with breastfeeding, upper lip tie is when the upper lip is tethered to the upper gum.
In older children and adolescents, an upper lip tie can be associated with a gap between the front teeth.
Though most infants have some degree of upper lip tie, when it becomes large and tight enough, it may prevent the upper lip from flaring out or curling up which is essential for breastfeeding in order to create an adequate seal with the breast. Also, some infants with upper lip tie will exhibit an upper lip crease with the skin turning pale in an attempt to flare up during breastfeeding.
If the upper lip tie is tight enough, an infant may have trouble feeding even from a bottle.
A good seal helps the baby draw the nipple deeply into the mouth and assists in the suck in order to swallow the milk produced by the breast. When a good seal is absent, an excessive amount of air is introduced into the baby’s mouth which is also swallowed along with the milk causing a too-gassy baby. Further, lack of a good seal makes it more difficult for the baby to maintain the nipple’s position in the mouth making for a prolonged and uncomfortable feeding.
Here are examples of an upper lip tie: