Babies get tongue-tie because of a minor glitch in fetal development: cells that should break down and release the tongue from the floor of the mouth don’t fully do their job. The result is an unusually short or tight band of tissue, called the lingual frenulum, that restricts the tongue’s movement. It affects roughly 2% to 10% of newborns depending on how strictly it’s defined, and it’s significantly more common in boys than girls.
What Happens During Development
Early in pregnancy, the tongue starts out fused to the bottom of the mouth. As the fetus grows, a natural process of programmed cell death gradually separates the tongue, freeing it to move independently. The lingual frenulum is simply the small strip of tissue left behind after that separation is complete.
In babies born with tongue-tie, that cell breakdown process stops too early or doesn’t happen thoroughly enough. The frenulum ends up thicker, shorter, or tighter than it should be, keeping the tongue anchored closer to the floor of the mouth. This isn’t caused by anything that goes wrong during labor or delivery. It happens weeks earlier, during the first trimester when the tongue and mouth are still forming.
Genetics Play a Major Role
Tongue-tie runs in families. In a pedigree study of 149 patients, about 39% had at least one relative with the same condition, and researchers traced the inheritance rate at roughly 21% across three generations. The remaining 61% of cases appeared to be sporadic, with no known family history.
The genetics aren’t straightforward, though. Some research points to X-linked inheritance, meaning the relevant gene sits on the X chromosome. This would explain why boys are affected far more often: one large study found a male-to-female ratio of 2.6 to 1. Boys have only one X chromosome, so a single copy of a variant gene is enough to cause the condition. Girls, with two X chromosomes, have a backup copy that can compensate.
A specific gene called TBX22 has been identified in some cases, particularly when tongue-tie appears alongside cleft palate. Mutations in this gene are linked to a syndrome called X-linked cleft palate, where tongue-tie is one of several features. Other researchers have suggested tongue-tie may sometimes follow an autosomal dominant pattern, meaning it can be passed down through either parent regardless of sex. The bottom line is that genetics clearly matter, but scientists haven’t pinpointed a single inheritance pattern that explains every case.
Tongue-Tie as Part of a Broader Condition
Most babies with tongue-tie are otherwise completely healthy. In a small number of cases, though, tongue-tie shows up as one feature of a larger genetic syndrome. These include Opitz syndrome, Beckwith-Wiedemann syndrome, Simpson-Golabi-Behmel syndrome, and orofaciodigital syndrome. Doctors typically recognize these syndromes by their other, more prominent features, so tongue-tie in these situations is usually caught as part of a broader evaluation rather than being the first thing noticed.
What About Folic Acid?
You may have seen claims that taking folic acid during pregnancy causes tongue-tie. The theory is that excess folic acid could lead to tighter closure of midline structures in the developing baby, resulting in extra connective tissue at the base of the tongue. A systematic review published in PLOS One looked for evidence supporting this idea and found only one relevant study, a case-control study with significant limitations including selection bias and unclear measurement of supplement intake. The review concluded there is no clear evidence linking folic acid supplementation to tongue-tie. Folic acid remains strongly recommended in pregnancy for preventing neural tube defects, and this theoretical concern does not change that guidance.
Types of Tongue-Tie
Not all tongue-ties look the same. Doctors use classification systems to describe the severity and location. In an anterior tongue-tie, the frenulum attaches near the tip of the tongue, creating the classic heart-shaped tongue appearance when the baby tries to stick it out. These are usually easy to spot visually.
Posterior tongue-ties attach further back, closer to the base of the tongue. They can be harder to see and are sometimes only noticed when a baby has trouble feeding. Classification systems grade tongue-tie from mild (a thin, slightly short frenulum) through moderate to severe or complete, where the tongue is essentially tethered to the floor of the mouth along most of its underside. The severity doesn’t always predict symptoms. Some babies with a visually obvious tongue-tie feed perfectly well, while others with a subtler restriction struggle significantly.
How It Affects Feeding
The most common problem linked to tongue-tie is difficulty breastfeeding. A baby needs to extend the tongue over the lower gum and cup it around the breast to latch effectively. When the frenulum restricts that movement, the baby may not be able to latch deeply enough, leading to inefficient milk transfer.
For the baby, signs include a shallow or weak latch, clicking sounds during feeding, poor weight gain, and feeding sessions that seem to go on endlessly without the baby being satisfied. For the nursing parent, the hallmark symptom is nipple pain. Because the baby compensates for limited tongue movement by clamping down harder with the gums, feedings can become extremely painful, and nipple damage like cracking or blistering is common. Not every baby with a visible tongue-tie will have these problems, but when breastfeeding difficulties persist despite good positioning and technique, tongue-tie is one of the things worth evaluating.
Why It Seems More Common Now
Diagnosis rates for tongue-tie have increased substantially in recent years. Studies focused on the United States, Canada, and England found that the frequency of diagnosis in newborns ranges from 1.7% to 10.7%, a wide spread that reflects genuine disagreement about where to draw the line between a normal frenulum and a problematic one. Part of the apparent increase is greater awareness among parents and healthcare providers, particularly as breastfeeding rates have risen and more attention is paid to latch problems. Part of it may also reflect broader diagnostic criteria catching milder cases that would have gone unnoticed in previous decades. The underlying biology hasn’t changed. What has changed is how carefully clinicians and lactation consultants are looking for it.