Tongue-tie (ankyloglossia) is a condition that restricts the tongue's range of motion.  The restriction is caused by a membrane (lingual frenulum) under the tongue being unusually short, thick or tight. There is also a membrane (labial frenulum) connecting the upper lip to the gums, which can cause a lip-tie depending on where it inserts into the gums.

Tongue and lip-ties can cause problems with breastfeeding:

  • Problems latching onto the nipple. Instead of sucking baby may be chewing on nipple with gums.
  • Difficulty creating or maintaining suction on the nipple.
  • Poor transfer of milk.
  • Digestive issues such as reflux.
  • Poor weight gain.  
  • Nipple and breast pain.

 Later in life tongue-ties may also lead to speech problems, crooked teeth, under/over development of the jaws leading to facial disharmony and a higher risk of dental cavities.

Diagnosing a tongue-tie involves more than merely noting the presence of a membrane beneath the tongue.  There are four classifications of tongue-ties.   And in fact in a Class 4 tongue-tie no membrane is visible beneath the tongue, yet this is the class most associated with breastfeeding issues.  Although various classes of tongue-ties may be diagnosed, only the ones functionally interfering with breastfeeding need to be corrected immediately.

http://www.drghaheri.com/blog/2014/3/22/rethinking-tongue-tie-anatomy-anterior-vs-posterior-is-irrelevant