Unilateral vs Bilateral Cleft Lip: What is the Difference?
At a Glance
A cleft lip is described by its location and severity. Unilateral means it affects one side of the lip, while bilateral affects both sides. An incomplete cleft is a partial separation that stops before the nose, whereas a complete cleft extends entirely through the lip and gum into the nostril.
In this answer
3 sections
Receiving a cleft lip diagnosis during a prenatal ultrasound can introduce parents to a lot of new medical terms very quickly. The clinical words used to describe a cleft lip simply tell doctors the location of the cleft (which side or sides it affects) and how far up the face the separation extends.
Understanding these terms can give you a much clearer picture of your baby’s diagnosis and what to expect.
Unilateral vs. Bilateral Cleft Lip: Which Side is Affected?
When your baby’s care team talks about laterality, they are describing whether the cleft affects one or both sides of the upper lip [1].
- Unilateral cleft lip: The word unilateral simply means “one side.” A unilateral cleft lip involves a separation on only one side of the philtrum (the vertical groove between the nose and the upper lip) [2][1]. Interestingly, when a cleft lip happens on just one side, it occurs most commonly on the left side of the face [3][4].
- Bilateral cleft lip: The word bilateral means “both sides.” In a bilateral cleft lip, there is a separation on both the left and right sides of the upper lip [2]. In these cases, the central part of the lip and gum (the premaxilla) might sit slightly forward because it is not attached to the sides [2].
Whether the cleft is unilateral or bilateral helps the surgical team plan the best approach for repair. For example, bilateral clefts sometimes require a different timeline or a two-stage approach compared to a single-stage unilateral repair [5][2].
Complete vs. Incomplete Cleft Lip: How High Does It Go?
Doctors also describe a cleft lip by its severity—meaning how far the separation reaches up toward the nose and whether it involves the gum line (the alveolus). This is what the terms complete and incomplete refer to [6][7].
- Incomplete cleft lip: An incomplete cleft is a partial separation. This can range from a small notch in the colored part of the lip (the vermilion) to a deeper separation that extends through the lip and slightly into the gum. However, the separation stops before it reaches the nostril. This means there is still a band of normal tissue (often called a Simonart’s band) connecting the bottom of the nose across the cleft [8][9]. Because there is less tissue deficiency, surgical repairs can often preserve more of the natural tissue [10][11].
- Complete cleft lip: A complete cleft extends all the way up through the upper lip, through the gum line (the alveolus, where the teeth will eventually emerge), and completely into the floor of the nostril (the nasal sill) [12]. This creates a full opening connecting the lip and the inside of the nose. Babies with a complete cleft lip often have more noticeable differences in the shape of their nose [13] and have a greater deficiency in soft tissue compared to those with incomplete clefts [8][9]. Because of this, babies with complete clefts may be given a specialized orthopedic appliance before surgery (like a nasoalveolar molding, or NAM device) to help gently reshape the gums and nasal cartilage before their surgical repair [13][14].
What This Means for Your Baby
Knowing whether your baby’s cleft is unilateral or bilateral, and complete or incomplete, allows your medical team to customize their care plan. The terms define the anatomical structure, but they don’t define your baby’s future. No matter the type, modern cleft repair techniques are highly advanced, focusing on achieving natural symmetry and excellent function [15][16].
Common questions in this guide
What is a unilateral cleft lip?
What does a bilateral cleft lip mean?
What is the difference between a complete and incomplete cleft lip?
What is a Simonart's band?
Will my baby need a nasoalveolar molding (NAM) device?
Questions to Ask Your Doctor
Curated prompts to bring to your next appointment.
- 1.Is there a band of tissue (Simonart's band) visible on the ultrasound, suggesting the cleft is incomplete?
- 2.Does the ultrasound show any involvement of the alveolus (gum line) or the palate, or just the lip?
- 3.Based on whether this is unilateral or bilateral, what might the timeline for surgical repair look like?
- 4.Will my baby be a candidate for a nasoalveolar molding (NAM) device before surgery?
- 5.Who should I be consulting with before birth to prepare for the specific type of cleft my baby has?
Questions For You
Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.
Related questions
References
References (16)
- 1
Cleft lip repair: are outcomes between unilateral and bilateral clefts comparable?
Chouairi F, Mets EJ, Torabi SJ, Alperovich M
Journal of plastic surgery and hand surgery 2020; (54(1)):29-32 doi:10.1080/2000656X.2019.1661848.
PMID: 31524555 - 2
Reversed Sequence of Cleft Repair: Palate First, Lip Second in Bilateral Cleft With Severely Protruded Premaxilla and Delayed Presentation.
Chaisrisawadisuk S, Tantipanichkul KO, Kosakarn N, Chaisrisawadisuk S
The Journal of craniofacial surgery 2025; (36(4)):1275-1277 doi:10.1097/SCS.0000000000011147.
PMID: 40310469 - 3
Cleft sidedness and congenitally missing teeth in patients with cleft lip and palate patients.
Jamilian A, Lucchese A, Darnahal A, et al.
Progress in orthodontics 2016; (17()):14 doi:10.1186/s40510-016-0127-z.
PMID: 27135068 - 4
An investigation into nutritional methods at the fifth day after birth of infants in association with cleft type and laterality.
Ogawa A, Sasaki Y, Naruse M
Congenital anomalies 2023; (63(3)):74-78 doi:10.1111/cga.12509.
PMID: 36680745 - 5
Trends of Staged Versus Single-Stage Operations for Bilateral Cleft Lip Repair: Analysis of a National Database.
Lee AD, Murphy M, Tin G, et al.
The Journal of craniofacial surgery 2025; (36(4)):1246-1248 doi:10.1097/SCS.0000000000011035.
PMID: 39878571 - 6
The Smile Index: Part 2. A Simple, Prognostic Severity Scale for Unilateral Cleft Lip.
Yao CA, McCullough M, Auslander A, et al.
Plastic and reconstructive surgery 2019; (143(4)):790e-797e doi:10.1097/PRS.0000000000005432.
PMID: 30921136 - 7
[New concepts, methods, and techniques for unilateral cleft lip repair].
Shi B
Hua xi kou qiang yi xue za zhi = Huaxi kouqiang yixue zazhi = West China journal of stomatology 2025; (43(3)):299-304 doi:10.7518/hxkq.2025.2025018.
PMID: 40523809 - 8
Unilateral Cleft Lip Repair Using the Chang Gung Technique: An Outcome Analysis.
Tangco I, Bhandari K, Yao CF, et al.
Annals of plastic surgery 2021; (86(2S Suppl 1)):S41-S45 doi:10.1097/SAP.0000000000002704.
PMID: 33438954 - 9
Philtral Height Discrepancy in Patients with Complete and Incomplete Cleft Lips + /-Palate - Results from a Single Nation Consecutive Cohort.
Rivers CM, Drake D, Devlin MF, Russell C
The Cleft palate-craniofacial journal : official publication of the American Cleft Palate-Craniofacial Association 2024; (61(6)):953-956 doi:10.1177/10556656221150874.
PMID: 36632018 - 10
The Preservation Technique for Incomplete Unilateral Cleft Lip Reconstruction.
Fell M, Breakey W, Benitez BK, et al.
Plastic and reconstructive surgery. Global open 2024; (12(9)):e6172 doi:10.1097/GOX.0000000000006172.
PMID: 39296618 - 11
Muscle reconstruction using a five-flap method with a short straight-line incision in unilateral incomplete cleft lip repair.
Diao JS, He L, Yu XY, et al.
International journal of oral and maxillofacial surgery 2024; (53(12)):997-1005 doi:10.1016/j.ijom.2024.07.017.
PMID: 39095303 - 12
Simonart's Band: Its Effect on Cleft Classification and Recommendations for Standardized Nomenclature.
Naran S, Kirschner RE, Schuster L, et al.
The Cleft palate-craniofacial journal : official publication of the American Cleft Palate-Craniofacial Association 2017; (54(6)):726-733 doi:10.1597/15-319.
PMID: 27618614 - 13
Effects of Active Presurgical Orthopaedics Appliances in Infants With Complete Unilateral Cleft Lip and 'T-Shaped' Alveolus: A Preliminary Study.
Nguyen TT, Ho TT, Nguyen DV, Huynh NC
Orthodontics & craniofacial research 2025; (28(2)):271-278 doi:10.1111/ocr.12870.
PMID: 39475444 - 14
Comparison of two treatment protocols in children with unilateral complete cleft lip and palate: Tridimensional evaluation of the maxillary dental arch.
Jorge PK, Gnoinski W, Vaz Laskos K, et al.
Journal of cranio-maxillo-facial surgery : official publication of the European Association for Cranio-Maxillo-Facial Surgery 2016; (44(9)):1117-22.
PMID: 27460947 - 15
Dynamic and static nasolabial muscle anatomy of unilateral cleft lip adult patients based on magnetic resonance imaging data.
Wang K, Li Y, Xia C, et al.
Hua xi kou qiang yi xue za zhi = Huaxi kouqiang yixue zazhi = West China journal of stomatology 2024; (42(5)):636-643 doi:10.7518/hxkq.2024.2024063.
PMID: 39304507 - 16
A new technique for perioral muscle reconstruction and lip lengthening in complete unilateral cleft lip.
Jung S, Chung KH, Chang SY, et al.
Journal of plastic, reconstructive & aesthetic surgery : JPRAS 2020; (73(4)):749-757 doi:10.1016/j.bjps.2019.11.013.
PMID: 31864889
This page explains cleft lip diagnoses for educational purposes only. Always consult with your pediatric craniofacial team to understand your baby's specific ultrasound results and customized treatment plan.
Get notified when new evidence is published on Cleft lip and alveolus.
We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.