Tongue-tie (ankyloglossia) is a short lingual frenulum that restricts tongue protrusion and may be present in up to 30% of babies.
Though most infants are asymptomatic, when severe it can interfere with latching and effective breast-feeding. Lactation support may resolve the problem but if not, tongue-tie division is indicated.
Reference: Cleminson, J., Oddie, S., Renfrew, M. J., & McGuire, W. (2014). Being baby friendly: evidence-based breastfeeding support. Archives of Disease in Childhood (Fetal Neonatal Edition); 100: F173-178.