07/31/2026
A Class 4 tongue tie is NOT “worse” than a Class 2.
This is one of the biggest misconceptions I see online, even among healthcare professionals.
Parents are often told, “It’s only a Class 2,” or, “It’s a severe Class 4.” The “class” of a tongue tie is not a severity ranking.
A classification system simply describes where the frenulum attaches or what it looks like. It does not always tell you how much the tongue can move, how well a baby can breastfeed, or whether treatment is needed.
Let’s break it down.
Kotlow Classification
The Kotlow system is probably the one most parents encounter online. It classifies tongue ties based primarily on the free tongue length, meaning the distance from where the frenulum inserts to the tip of the tongue. The shorter the free tongue, the higher the class.
* Class I – Mild
* Class II – Moderate
* Class III – Severe
* Class IV – Complete
Although these labels use words like “mild” and “severe,” they refer only to anatomical appearance, not functional impairment. A baby with a Class IV tongue tie may breastfeed beautifully, while another with a Class II may struggle tremendously. The problem is that anatomy and function don’t always match.
Coryllos Classification
Another commonly used system is the Coryllos classification. Rather than measuring free tongue length, it categorizes tongue ties based on where the frenulum inserts under the tongue and whether the frenulum is more anterior or posterior. Again, this is simply a description of anatomy. It tells us where the tissue is located, not how restrictive it is.
Hazelbaker Assessment Tool (HATLFF)
The Hazelbaker Assessment Tool for Lingual Frenulum Function takes a different approach.
Instead of looking only at appearance, it evaluates both:
* Appearance of the frenulum
* Function of the tongue
The functional portion looks at things like tongue lift, lateralization, extension, cupping, spread, and peristaltic movement. This is much closer to what actually matters clinically because feeding depends on movement, not simply appearance.
Even so, the Hazelbaker tool has limitations. It was originally developed to assist in breastfeeding assessments, requires training for reliable scoring, and should never replace a comprehensive feeding evaluation.
Other Assessment Tools
Several newer tools attempt to improve assessment by incorporating function.
The Bristol Tongue Assessment Tool (BTAT), later refined into the TABBY pictorial tool, was designed to improve consistency among clinicians. Other assessment methods combine structured examination with direct observation of breastfeeding or bottle feeding.
Each tool has strengths and weaknesses. None should be used in isolation.
What Actually Determines Severity? This is the most important point. Severity is determined by restriction of movement, not by class.
When I evaluate an infant, I’m asking questions like:
* Can the tongue elevate to the palate?
* Can it extend beyond the lower gum?
* Can it lateralize from side to side?
* Can it cup around the breast or bottle ni**le?
* Does it create and maintain an effective seal?
* Can it generate suction without compensations?
* Does it move with smooth, coordinated peristaltic motion?
* What do the other oral structures look like?
*What does the rest of the body look like?
I’m also looking at what happens during feeding.
* Is milk transferring effectively?
* Is the parent experiencing ni**le pain or tissue damage?
* Is the baby swallowing efficiently?
* Is there excessive clicking or loss of suction?
* Is weight gain appropriate?
* Is feeding exhausting for the baby?
These findings tell us far more than a class number ever could. Appearance doesn’t equal function
I’ve seen babies with what would be called a Class IV tongue tie breastfeed beautifully because the tissue was remarkably elastic and allowed excellent mobility. I’ve also seen babies with a small anterior frenulum who had profound restriction because the tissue was thick, inelastic, and tethered the tongue from moving in multiple directions.
The frenulum itself varies enormously between individuals.
Things that influence restriction include:
* Tissue elasticity
* Thickness
* Length
* Depth of attachment
* Fascial involvement
* Surrounding muscle tension
* Oral motor coordination
* Overall infant biomechanics
This is why two babies with identical “classes” may have completely different feeding experiences.
We need to treat the whole baby and not just a class number. A tongue tie assessment should never end with someone saying, “It’s a Class 3.”
That’s simply describing anatomy.
A comprehensive evaluation looks at:
* Tongue mobility in every direction
* Infant oral motor function
* Breastfeeding or bottle-feeding mechanics
* Milk transfer
* Maternal symptoms
* Infant symptoms
* Overall feeding goals
Sometimes a highly restrictive frenulum causes no feeding problems and doesn’t require intervention. Other times, what appears to be a “minor” tie significantly limits tongue movement and contributes to pain, poor milk transfer, prolonged feeds, or inadequate weight gain.
The decision to perform a frenotomy should be based on functional impairment, not on the class of the frenulum alone.
The next time someone tells you your baby has “only a Class 2” or “a severe Class 4,” remember:
A classification describes anatomy. Restriction describes function.
And in feeding, function is what matters most.
