“Hair lip” is a common misspelling and older folk term for cleft lip, a birth defect where the upper lip doesn’t fully form before birth. The correct medical term is cleft lip, sometimes occurring alongside cleft palate (an opening in the roof of the mouth). About 1 in 3,300 babies are born with a cleft lip, making it one of the most common birth defects worldwide.
Why It’s Called a “Hair Lip”
The term “hair lip” (sometimes spelled “harelip”) dates back centuries and referred to the resemblance between a cleft in a person’s upper lip and the split upper lip of a hare, or rabbit. The term is now considered outdated and offensive. The medical community and advocacy organizations use “cleft lip” exclusively, and most style guides discourage “harelip” in any context.
What a Cleft Lip Looks Like
A cleft lip is an opening or split in the upper lip that forms during early pregnancy. It can range from a small notch in the lip to a gap that extends all the way through the upper gum and into the bottom of the nose. The split can appear on just one side of the lip (unilateral) or on both sides (bilateral).
Cleft lip and cleft palate are related but separate conditions. Some babies have only a cleft lip, some have only a cleft palate, and some have both. When the palate is also involved, there’s an opening in the roof of the mouth that connects the oral and nasal cavities.
How a Cleft Forms During Pregnancy
Between the 6th and 11th week of pregnancy, tissues from each side of a baby’s head grow toward the center of the face and fuse together to form the lips and mouth. A cleft lip happens when this tissue doesn’t join completely. The cause is usually a combination of genetic and environmental factors rather than any single thing a parent did or didn’t do.
Known risk factors include a family history of clefts, smoking during pregnancy, diabetes, and certain medications taken during early pregnancy. When one child in a family is born with a cleft lip, the risk for a subsequent sibling rises from roughly 0.1% in the general population to about 3 to 5%. In families where a first-degree relative (parent or sibling) is affected, recurrence rates can be higher still.
How a Cleft Lip Is Detected
Cleft lip can often be spotted on a routine ultrasound during pregnancy, though detection rates vary widely. At the standard 20-week anatomy scan, sensitivity ranges from 16% to 93% depending on the severity of the cleft and the equipment used. Complete clefts involving both the lip and palate are caught about 93% of the time, while a small, one-sided notch in the lip may not be visible until after 27 weeks. Isolated cleft palate, with no visible lip involvement, is the hardest to detect prenatally, picked up in only about 22% of cases.
Three-dimensional ultrasound improves accuracy, particularly for evaluating the palate once a cleft lip has been identified on a standard scan. Many clefts, especially milder ones, are first noticed at birth.
Feeding a Baby With a Cleft Lip
One of the first practical challenges parents face is feeding. A gap in the lip or palate can make it difficult for a baby to create the suction needed for breastfeeding or standard bottle-feeding. Milk may flow into the nasal cavity, causing coughing or sputtering.
Several adaptations help. Holding the baby at a 45-degree angle (sometimes called a modified football hold) reduces nasal regurgitation. Specialty bottles with squeezable sides or soft, wide-based nipples help deliver milk without requiring strong suction. For babies with a cleft palate, a feeding obturator, a small custom-made plate that covers the gap in the roof of the mouth, can create a seal between the oral and nasal cavities and make feeding much easier. Most cleft teams will fit one of these devices shortly after birth.
Surgical Repair and Timing
Cleft lip is repaired surgically, typically when a baby is around 10 weeks old. Surgeons traditionally follow what’s known as the “rule of 10s”: the infant should be at least 10 weeks of age, weigh at least 10 pounds, and have a hemoglobin level of at least 10 grams per deciliter. These benchmarks help ensure the baby is strong enough to tolerate anesthesia and heal well.
The surgery closes the gap in the lip and reshapes the nose if needed. For most children, the initial lip repair is a single procedure, though some may need minor revisions later as the face grows. If a cleft palate is also present, that repair is usually a separate surgery performed between 9 and 18 months of age.
Long-Term Health Effects
Even after surgical repair, children born with a cleft lip may need ongoing care for related issues. In a study of children with cleft lip only (no palate involvement), 62% had dental or bite abnormalities. Extra teeth growing in near the cleft site were the most common dental issue, and crossbite (where upper and lower teeth don’t align properly) was the most frequent bite problem. Orthodontic treatment is common and often begins in childhood.
About a third of children with cleft lip experienced fluid buildup in the middle ear, which can affect hearing if untreated. Speech and language delays were less common in children with cleft lip alone, affecting 13% and 18% respectively, but rates are significantly higher when the palate is also involved.
The Care Team
Children with cleft lip typically see a coordinated group of specialists rather than a single doctor. This team usually includes a plastic or craniofacial surgeon, an orthodontist, a speech-language pathologist, an audiologist to monitor hearing, and an ear, nose, and throat specialist. Depending on the child’s needs, a pediatric dentist, psychologist, or social worker may also be involved. This team approach continues from infancy through adolescence, with the specific focus shifting as the child grows: feeding support early on, speech therapy in toddlerhood, orthodontics in the school years, and sometimes a final surgical revision in the teens once facial growth is complete.