“Harelip disease” is an old word for a birth difference where the upper lip does not join together in the middle before birth. Today doctors say cleft lip instead, because “harelip” is now seen as hurtful and disrespectful. A cleft lip can be a small notch in the lip or a wide opening that goes up toward the nose. It can happen on one side of the lip (unilateral) or on both sides (bilateral). Sometimes it also involves the bone of the upper gum and the front part of the roof of the mouth.
“Harelip” is an older name for cleft lip. Cleft lip is a birth condition where the upper lip does not join fully while a baby is growing in the womb. The opening can be small (a tiny notch) or large (a wide split) and may be on one side or both sides. It can happen alone or together with a cleft palate (an opening in the roof of the mouth). In many babies, the exact cause is not known, and it may come from a mix of genes and pregnancy factors.
This problem starts early in pregnancy when parts of the baby’s face are forming. Normally, tissues of the upper lip grow from the sides and meet in the middle. In cleft lip, these tissues do not fully join, so a gap stays open.
Because the old word “harelip” compares people to animals, many people with cleft lip feel it is insulting. Health groups and cleft support groups strongly advise using “cleft lip” or “cleft lip and palate” instead.
Other names
Cleft lip has several other names or phrases that people may use:
“Cleft lip” is the most correct and respectful modern medical term.
“Cleft lip and palate” is used when the split in the lip happens together with a split in the roof of the mouth.
“Orofacial cleft” is a broader term that includes cleft lip, cleft palate, or both, and is often used in research papers.
“Labial cleft” is a more technical phrase sometimes used by surgeons, meaning a cleft of the lip.
“Non-syndromic cleft lip” is used when the cleft lip happens alone, without other birth defects or genetic syndromes.
Types of cleft lip
There are several common types of cleft lip, based on how wide the opening is and where it is. Doctors often describe them like this:
Unilateral incomplete cleft lip means the cleft is on one side of the lip and does not go all the way into the nose. It may look like a notch or partial split.
Unilateral complete cleft lip means the cleft is on one side and goes from the lip all the way into the nostril, often affecting the shape of the nose and upper gum.
Bilateral incomplete cleft lip means there are splits on both sides of the lip, but they do not fully reach the nose. The center part of the lip is still partly attached.
Bilateral complete cleft lip means there are wide clefts on both sides, extending into both nostrils. The middle segment of the lip and gum can look like a small separate piece.
Cleft lip with cleft palate means the split in the lip is joined with a split in the hard and/or soft palate, affecting the roof of the mouth as well as the lip.
Causes and risk factors
Cleft lip usually has many causes together. Most cases are from a mix of genes and environmental factors, not just one single cause.
1. Family history of cleft lip
If a parent or close relative has a cleft lip or palate, the baby’s risk is higher. This shows that genes play a strong role.
2. Specific genetic syndromes
More than 300 genetic syndromes include cleft lip or palate as part of their features, such as some chromosomal or single-gene conditions.
3. Gene–environment interaction
Some babies have genes that make them more sensitive to things like cigarette smoke or certain medicines, so these exposures increase their cleft risk more than in other babies.
4. Maternal smoking during pregnancy
Smoking while pregnant is one of the best-proven risk factors. Toxins in smoke can disturb the normal growth of the baby’s face.
5. Maternal alcohol use
Heavy use of alcohol in pregnancy can damage the developing baby and is linked with cleft lip and palate, especially in the setting of fetal alcohol spectrum disorders.
6. Lack of folic acid (vitamin B9)
Not taking folic acid supplements and having a low-folate diet during early pregnancy is linked with more cases of cleft lip and palate.
7. Poor overall maternal nutrition
Mothers who are under-nourished or have low intake of key vitamins and minerals have a higher chance of babies with orofacial clefts.
8. Maternal obesity
Some studies show that being obese before pregnancy or early in pregnancy is related to a higher risk of cleft lip and palate.
9. Maternal diabetes
Pregnant women with poorly controlled diabetes have a higher risk of several birth defects, including cleft lip and palate.
10. Certain anti-seizure medicines
Some anticonvulsant drugs, such as older medicines like phenytoin or valproate, are linked to a higher rate of cleft lip and other defects when taken in early pregnancy.
11. Retinoic acid (vitamin A derivatives)
High doses of retinoic acid (used in some acne drugs) during pregnancy can disturb facial development and increase cleft risk.
12. Other teratogenic drugs and chemicals
Exposure to some other medicines, industrial chemicals, or pesticides that affect fetal development may contribute to cleft lip in susceptible families.
13. Maternal infections in early pregnancy
Some infections during the first trimester, such as rubella or other systemic viral illnesses, have been associated with facial malformations including clefts.
14. Maternal fever or hyperthermia
High body temperature from severe fever or hot tub/sauna exposure in early pregnancy may interfere with normal tissue fusion in the face.
15. Advanced maternal age
Pregnancies at older maternal ages sometimes carry more risk for congenital anomalies, including cleft lip and palate.
16. Low maternal age with high-risk exposures
Very young mothers who also smoke, drink, or have poor diet may have increased risk due to combined social and biological factors.
17. Low socioeconomic status
Poverty can lead to less access to healthy food, supplements, prenatal care, and counseling about medicines, which can increase the chance of cleft.
18. Environmental pollution
Living close to heavy traffic, factories, or agricultural chemicals may expose pregnant women to pollutants that have been linked in some studies to orofacial clefts.
19. Consanguineous marriage (parents related by blood)
Marriages between close relatives can increase the chance of recessive genetic changes, and some populations with more consanguinity show higher cleft rates.
20. Unknown or idiopathic causes
In many babies, no clear cause or risk factor can be found even after careful testing. In these cases, doctors say the cleft is idiopathic or multifactorial, meaning it comes from a complex mix of genes and environment.
Symptoms and signs
1. Visible gap in the upper lip
The main sign is a split, notch, or opening in the upper lip that can be small or very wide. It may affect one side or both sides of the lip.
2. Distorted shape of the nostril
In complete cleft lip, the nostril on the affected side is often flattened or pulled upward, and the nasal tip can look twisted.
3. Opening in the gum or upper jaw
The cleft may extend into the upper gum and the bone under it, leaving a gap where the teeth should come in later.
4. Feeding difficulty in newborns
Some babies cannot make a good seal on the breast or bottle, so milk leaks out or they take a long time to feed. Feeding problems are worse when cleft palate is also present.
5. Milk coming out of the nose
If the cleft involves the palate, milk can flow from the mouth up through the nose because the mouth and nose are not fully separated.
6. Poor weight gain or failure to thrive
Because feeding is harder, some babies do not gain weight well and may fall below their expected growth curves if feeding support is not given.
7. Frequent ear infections
Cleft palate can affect the muscles that open the eustachian tube, so fluid collects in the middle ear and infections happen often.
8. Hearing loss
Long-term middle ear fluid and infections can reduce hearing. Some children need ear tubes and regular hearing checks.
9. Nasal-sounding or unclear speech
If the palate is not repaired early enough, air escapes through the nose when the child talks, giving a nasal voice and making some sounds difficult to pronounce.
10. Dental problems
Teeth near the cleft may be missing, extra, crooked, or poorly formed, and the upper jaw may be narrow or pushed back.
11. Difficulty with blowing, whistling, or sucking
Children with a cleft may struggle to blow up balloons, whistle, or use straws because they cannot build strong pressure inside the mouth.
12. Facial growth differences
Some children develop mid-face retrusion (flat upper jaw) or asymmetry of the nose and lip as they grow, especially if the cleft is severe.
13. Social and emotional problems
Visible facial differences and speech problems can lead to teasing, bullying, low self-esteem, or social anxiety if support is not given.
14. Sleep and breathing issues
In some cases, changes in the nose and jaw, or scarring from surgeries, may narrow the airway and contribute to snoring or breathing difficulty during sleep.
15. Associated anomalies in syndromic cases
When cleft lip is part of a syndrome, the baby may also have heart defects, limb problems, or other organ issues that must be checked.
Diagnostic tests
Cleft lip is often easy to see at birth, but doctors still do several tests to understand the full problem, check hearing and feeding, and look for other conditions. Some tests are done before birth, and some after birth.
Physical exam tests
1. Full newborn physical examination
Right after birth, the doctor checks the baby from head to toe. They look at the lip, nose, mouth, limbs, heart, and other organs to see if the cleft is isolated or part of a larger syndrome.
2. Detailed head and face examination
The doctor carefully inspects the shape of the lip, nostrils, upper jaw, and eyes. They note if the cleft is unilateral or bilateral, complete or incomplete, and whether the nose or mid-face is affected.
3. Intraoral (inside mouth) examination
A light and tongue depressor are used to look inside the mouth. The doctor checks the hard and soft palate, uvula, gums, and teeth (if present) to see if there is a cleft palate or gum involvement.
4. Growth and nutrition assessment
Weight, length, and head size are measured and compared with growth charts. If the baby is not gaining weight as expected, this points to feeding difficulty and the need for special feeding support.
Manual tests
5. Palpation of lip and gum margin
The doctor gently feels the edges of the lip and upper gum with gloved fingers. This helps them feel how wide the cleft is, how much bone is missing, and how the tissues move, which is important for surgical planning.
6. Palpation of the hard palate
With a gloved finger, the clinician feels along the roof of the mouth to check for hidden or “submucous” clefts that might not be obvious just by looking.
7. Functional suck and swallow assessment
A specialist, often a speech-language pathologist or feeding therapist, watches the baby during feeding. They feel the jaw and cheeks and check how well the baby can suck, swallow, and coordinate breathing during a feed.
8. Speech articulation assessment (in older children)
When the child is old enough to talk, a speech therapist listens while the child says certain sounds and words. They may feel the cheeks and throat to see if air leaks through the nose or if some sounds are difficult.
Lab and pathological tests
9. Basic blood tests for general health
Simple blood tests such as full blood count and biochemistry are done before surgery to check the child’s general health, look for anemia, and see if it is safe to give anesthesia.
10. Genetic counseling and family history review
A genetics doctor or counselor takes a detailed three-generation family history and reviews medical records to see if the cleft might be part of a hereditary pattern. This is not a lab test itself but guides further testing.
11. Chromosomal analysis (karyotype)
If the baby has other anomalies (for example heart defects or limb problems), blood may be taken to study the chromosomes. This can detect conditions such as trisomies or other chromosomal rearrangements.
12. Targeted genetic panels or exome testing
In suspected syndromic cleft or in families with more than one affected child, more detailed DNA tests can look for specific gene changes known to cause cleft lip and palate.
13. Prenatal blood tests with ultrasound correlation
In pregnancy, if a cleft is seen on ultrasound, parents may be offered maternal blood tests and, in some settings, invasive sampling (like chorionic villus sampling) combined with genetic analysis to check for associated syndromes.
Electrodiagnostic tests
14. Brainstem auditory evoked response (BAER) test
This hearing test uses small electrodes on the baby’s head to measure how the brain responds to sounds. It helps detect hearing loss in babies with cleft palate who cannot do standard hearing tests yet.
15. Tympanometry with acoustic reflex testing
Although partly mechanical, this test uses sound and pressure changes to see how well the eardrum and middle ear move. It helps confirm fluid build-up behind the eardrum, which is common in children with cleft palate.
16. Detailed audiometry in older children
When the child is older, they can do pure-tone audiometry or play audiometry. Headphones and sound signals are used, and responses are measured to map out hearing levels across different pitches.
17. Nerve function tests in rare cases
In unusual situations where facial nerve weakness is suspected, doctors may use electrical tests such as nerve conduction studies or electromyography to see how well the facial muscles and nerves are working.
Imaging tests
18. Prenatal 2D ultrasound
Standard two-dimensional ultrasound during mid-pregnancy can often show a cleft lip, especially when the sonographer looks carefully at the baby’s face in profile and front views.
19. Prenatal 3D ultrasound
Three-dimensional ultrasound gives a more detailed view of the baby’s face, making it easier to see the exact shape of the lip and nose, and sometimes the palate. It is used as a follow-up when a cleft is suspected on 2D scan.
20. Prenatal MRI (magnetic resonance imaging)
In some high-risk pregnancies or complex cases, MRI of the fetus may be used along with ultrasound to get more detail about the palate, brain, and other structures, without using radiation.
21. Postnatal skull and dental X-rays
As the child grows, dentists and orthodontists may take X-rays of the teeth, jaws, and skull to plan dental and jaw treatment. These images show missing teeth, jaw position, and how the cleft area is growing.
22. CT scan of the face and jaws
A CT scan gives 3D images of the bones of the face and maxilla (upper jaw). It is helpful for planning major surgeries, such as bone grafting to the gum or later jaw surgery in teenagers.
23. Nasendoscopy or video-fluoroscopy of the palate (functional imaging)
For children who still have speech problems after surgery, doctors may use a small camera through the nose or moving X-ray pictures during speech to see how the palate moves and where air is leaking.
