Cleft palate has a strong genetic component, with twin studies estimating that roughly 90% of the variation in risk traces back to inherited factors. But “genetic” does not mean “inevitable” or “simple.” Most cases arise from the combined effects of multiple genes interacting with environmental exposures during a narrow window of fetal development, and even identical twins sharing the same DNA are only concordant for clefting about a third to half the time. The story of cleft palate risk is one of probability shaped by family history, maternal health, and sometimes pure chance in how a developing face comes together.
How the Palate Forms and What Goes Wrong
The roof of your mouth forms in the first trimester, through a sequence of events that has to go right in the right order. Two tissue shelves grow out from what will become the upper jaw, initially hanging vertically on either side of the developing tongue. They then flip upward to a horizontal position, meet at the midline, and fuse together to create the barrier between the mouth and the nasal cavity. A disruption at any stage of that process can leave an opening.
1PubMed Central. Molecular and Cellular Mechanisms of Palate DevelopmentThe shelf-elevation step is especially vulnerable. Animal studies have shown that the shelves rise rapidly thanks to an internal pressure generated by water binding to sugary molecules in the tissue. If production of those molecules is disrupted, the shelves may not elevate properly, and fusion never happens.
2PubMed. The mechanism of palatal shelf elevation and the pathogenesis of cleft palateSignaling pathways also play a direct role in the final fusion step. In mouse studies, disrupting a specific signaling pathway in the palate’s surface layer prevents the middle seam from dissolving, which is exactly what needs to happen for the two shelves to merge into one continuous roof. Without that dissolution, a cleft remains.
3PubMed Central. Epithelial Wnt/β-catenin signaling regulates palatal shelf fusion through regulation of Tgfβ3 expressionWhat Twin Studies Tell Us About Heritability
The strongest evidence for a genetic basis comes from comparing identical twins (who share all their DNA) with fraternal twins (who share about half). A large study using Danish registries found that when one identical twin had a cleft lip with or without cleft palate, the other twin was affected about 50% of the time. For fraternal twins, that figure dropped to roughly 8%. For isolated cleft palate specifically, the concordance was about 33% in identical twins versus 7% in fraternal twins. Statistical modeling put the heritability at around 90% for both cleft types, meaning genetics accounts for the vast majority of why some people develop clefts and others do not.
4PubMed Central. Risk of Oral Clefts in twinsThat 90% figure might sound like the case is closed, but the 50% concordance in identical twins is the telling detail. If clefting were purely genetic, identical twins would match nearly every time. The fact that they often do not points to environmental factors or random developmental variation tipping the balance. Researchers have confirmed this pattern independently: even with a strong genetic component, about half of identical twin pairs are discordant for clefting.
5PubMed Central. Copy number variation analysis of twin pairs discordant for cleft lip with or without cleft palateGenes That Raise the Risk
No single “cleft palate gene” explains most cases. Instead, researchers have identified dozens of genes that each contribute a small amount of risk. Among the best-studied are IRF6, MSX1, and PAX9, all of which are active in building the face and teeth during early development. Specific variants in the IRF6 gene have been significantly associated with non-syndromic cleft lip with or without palate, and certain combinations of IRF6 and PAX9 variants together increase risk further.
6PubMed. SNPs and interaction analyses of IRF6, MSX1 and PAX9 genes in patients with non‑syndromic cleft lip with or without palateThe field keeps expanding. A recent large-scale mouse screen examined nearly 500 gene knockouts and found 76 that produced cleft palates, with 44 of those never previously linked to clefting. That discovery underscores how many genetic contributors remain to be found.
7PubMed Central. Identification of novel genes regulating the development of the palateSyndromic Versus Non-Syndromic Clefts
About 70% of cleft lip cases and roughly half of isolated cleft palate cases are “non-syndromic,” meaning the cleft occurs on its own without other developmental problems. The remaining cases are syndromic, appearing as one feature of a broader genetic condition. The distinction matters because syndromic clefts tend to follow clearer inheritance patterns, while non-syndromic clefts are governed by the messier interplay of many genes and environmental factors.
Van der Woude syndrome is the most common syndromic form, accounting for about 2% of all orofacial cleft cases. It follows an autosomal dominant pattern, meaning a single copy of the gene variant from one parent is enough to cause it. Its hallmark features are small pits in the lower lip alongside a cleft lip, cleft palate, or both.
8PubMed Central. Van der Woude syndrome- a syndromic form of orofacial cleftingOther syndromes frequently associated with cleft palate include 22q11.2 deletion syndrome (sometimes called DiGeorge syndrome), Stickler syndrome, CHARGE syndrome, Treacher Collins syndrome, and Kabuki syndrome. A 20-year review of speech outcomes in syndromic cleft palate patients found these were the most commonly represented conditions.
9PubMed. A Comparison of Speech Outcomes Among Patients With Syndromic Cleft Palate: A 20-year ReviewPierre Robin sequence deserves special mention because it is sometimes mistaken for a standalone syndrome when it is really a cascade of events. It involves a small lower jaw, a tongue that falls backward, and a cleft palate. Research has linked some cases to disruption of the SOX9 and KCNJ2 genes, though Pierre Robin can also appear as part of several different syndromes.
10PubMed Central. Pierre Robin sequence may be caused by dysregulation of SOX9 and KCNJ2Environmental Factors During Pregnancy
Genetics loads the gun, but certain exposures during the first trimester can pull the trigger. Maternal smoking is the most extensively studied environmental risk factor. A meta-analysis of 11 studies found that smoking in the first trimester raised the odds of cleft lip with or without palate by about 29% and cleft palate alone by about 32%.
11PubMed. Maternal cigarette smoking and oral clefts: a meta-analysisThere is evidence of a dose-response relationship for cleft lip specifically. One study found the risk climbed from roughly 60% higher with passive smoke exposure up to about 90% higher for mothers smoking more than 10 cigarettes a day, though the link with isolated cleft palate was weaker in that particular analysis.
12PubMed Central. Maternal smoking and oral clefts: The role of detoxification pathway genesCertain medications taken during early pregnancy also appear to increase risk. A large study found small but statistically significant associations with several drug classes: anticonvulsants like topiramate and lamotrigine, common antidepressants including fluoxetine and sertraline, corticosteroids such as betamethasone and dexamethasone, and some antibiotics including amoxicillin and doxycycline.
13PubMed. Association of Commonly Prescribed Antepartum Medications and Incidence of Orofacial CleftingCorticosteroids have drawn particular attention. One case-control study found a substantially elevated risk of cleft lip with or without palate in infants whose mothers used corticosteroids during the first trimester, leading the authors to recommend restricting their use to situations where no safer alternative exists.
14Teratology. Corticosteroids during pregnancy and oral clefts: A case-control studyOne environmental exposure that has been investigated but does not appear to be a major factor is organic solvent exposure. A study comparing mothers of cleft cases with controls found that while chlorinated solvents were linked to neural tube defects, no solvent class was strongly associated with orofacial clefts.
15Occupational and Environmental Medicine. Maternal occupational exposure to organic solvents during early pregnancy and risks of neural tube defects and orofacial cleftsWhen Genes and Environment Collide
Some of the most interesting findings involve gene-environment interactions, where a genetic variant only becomes dangerous in combination with an environmental exposure. A meta-analysis examined a variant in the TGFA gene (which encodes a growth factor involved in tissue development) and found that among non-smoking mothers, the variant did not raise cleft palate risk at all. But when mothers smoked, infants carrying that variant had about twice the odds of cleft palate.
16PubMed. Oral clefts, maternal smoking, and TGFA: a meta-analysis of gene-environment interactionA separate study found that for mothers who smoked 20 or more cigarettes daily, infants carrying the uncommon TGFA variant faced three- to eleven-fold increased risks across different cleft types. That range is strikingly large compared to the modest 30% increase from smoking alone, illustrating how a genetic vulnerability can dramatically amplify an environmental hazard.
17PubMed Central. Orofacial clefts, parental cigarette smoking, and transforming growth factor-alpha gene variantsThe Role of Folic Acid
Folic acid supplementation around conception is one of the few actionable ways to reduce cleft risk. A meta-analysis combining five prospective studies found that folic acid-containing supplements cut the risk of cleft lip with palate roughly in half, though the effect on isolated cleft palate was less clear.
18PubMed. Folic acid-containing supplement consumption during pregnancy and risk for oral clefts: a meta-analysisA more recent study in a Chinese population found similarly striking results, with periconceptional folic acid supplementation associated with roughly 60% lower odds of non-syndromic cleft lip with or without palate. Starting supplementation before conception appeared to extend some protection to isolated cleft palate as well, though the overall link with cleft palate alone was not statistically significant.
19Scientific Reports. Maternal periconceptional folic acid supplementation reduced risks of non-syndromic oral clefts in offspringAn earlier study found a 25-50% risk reduction depending on the cleft type, though the authors cautioned the benefit might not come from folic acid alone. Women who take multivitamins tend to differ in other health behaviors, and the other vitamin components might contribute as well.
20The Lancet. Periconceptional multivitamin use and the occurrence of orofacial cleftsFamily Recurrence Risks in Real Numbers
For families who already have one child with a cleft, the question of recurrence is often the most pressing. A large Danish cohort study tracking more than 54,000 relatives of people with oral clefts provided some of the best available estimates. For a child born with cleft lip and palate, the recurrence risk for a first-degree relative (parent, sibling, or child) was about 3.5%. For second-degree relatives like aunts, uncles, and grandchildren, the risk dropped to roughly 0.8%, and for third-degree relatives it fell further to about 0.6%.
21PubMed Central. A cohort study of recurrence patterns among more than 54,000 relatives of oral cleft cases in Denmark: support for the multifactorial threshold model of inheritanceThe severity of the original cleft also mattered. Siblings of someone with bilateral cleft lip and palate (the more severe form) had about a 4.6% recurrence risk, versus 2.5% for siblings of someone with a unilateral defect. This pattern, where more severe cases predict higher family risk, fits a model in which a greater “genetic load” is required to produce a more severe cleft, and that heavier load is more likely to be partially shared among relatives.
21PubMed Central. A cohort study of recurrence patterns among more than 54,000 relatives of oral cleft cases in Denmark: support for the multifactorial threshold model of inheritanceIsolated cleft palate shows a slightly different pattern. In a separate Danish analysis, first-degree relatives of people with non-syndromic isolated cleft palate had about a 2.7% recurrence risk. But that risk dropped sharply for more distant relatives, falling to about 0.3% for second-degree relatives and essentially zero for third-degree relatives in the studied cohort.
22PubMed Central. Familial recurrence-pattern analysis of nonsyndromic isolated cleft palate–a Danish Registry studyRacial and Ethnic Variation in Prevalence
Cleft rates vary substantially across populations, which further underscores the genetic contribution. A 12-year U.S. study found that Native American and Alaska Native infants were roughly 44% more likely to have cleft lip with or without palate and 36% more likely to have isolated cleft palate compared to non-Hispanic white infants. Meanwhile, non-Hispanic Black and Asian/Pacific Islander infants had significantly lower rates of cleft lip (about 36-37% lower odds), and non-Hispanic Black, Asian/Pacific Islander, and Hispanic infants all showed lower rates of cleft palate alone.
23PubMed. 12-Year Trends of Orofacial Clefts in the United States: Highlighting Racial/Ethnic Differences in Prevalence of Cleft Lip and Cleft PalateGlobally, orofacial clefts arise in about 1.7 per 1,000 live births, but the rate varies with geography and ethnicity.
24The Lancet. Orafacial cleftsParental Age as a Risk Factor
Both older mothers and older fathers contribute to cleft risk, though in slightly different ways. A large U.S. study found that each additional year of paternal age was associated with a small but significant increase in the odds of cleft palate specifically. The relationship between paternal age and orofacial clefts was also modified by maternal age, meaning the combination of both parents’ ages matters more than either one alone.
25PubMed Central. Association of Paternal Age and Risk for Major Congenital Anomalies from the National Birth Defects Prevention Study, 1997–2004A Scandinavian study painted a similar picture: both maternal and paternal age were linked to cleft lip with or without palate, with each parent’s contribution depending on the age of the other. For isolated cleft palate, though, only paternal age remained a risk factor once both parents’ ages were analyzed together.
26Epidemiology. Parent’s Age and the Risk of Oral CleftsEpigenetics and the Missing Heritability Problem
Known gene variants explain only a fraction of cleft palate’s heritability, which has pushed researchers toward epigenetics, the study of chemical modifications that alter how genes are read without changing the DNA sequence itself. One key modification is DNA methylation, which acts like a dimmer switch on gene activity. Studies in both humans and mice have found that abnormal methylation patterns are involved in non-syndromic cleft lip and palate, with both too much and too little methylation potentially raising risk depending on which gene and tissue type is involved.
27PubMed Central. Alterations in DNA Methylation in Orofacial CleftsA 2024 mouse study demonstrated this connection directly. Researchers showed that the enzyme responsible for maintaining DNA methylation was active throughout palate development. When they knocked out that enzyme in the cells that build facial connective tissue during the earliest stage of palate outgrowth, the mice developed cleft palates. Disrupting the enzyme later, during shelf elevation and elongation, did not cause clefts. This suggests there is a critical window during which methylation must function correctly, and environmental exposures that disturb methylation during that window could contribute to clefting.
28PubMed Central. Disruption of DNA methylation-mediated cranial neural crest proliferation and differentiation causes orofacial clefts in miceThe epigenetic angle is significant because it provides a plausible bridge between genetics and environment. Factors like maternal nutrition, smoking, and medication use can all influence methylation, which means they may raise cleft risk not by damaging DNA directly but by altering how existing genes are expressed during the critical weeks of palate formation.
29PubMed Central. Developmental epigenetics of the murine secondary palatePrenatal Detection and Its Limits
Cleft lip is far easier to spot on a prenatal ultrasound than cleft palate. A systematic review found that standard two-dimensional ultrasound detected cleft lip with or without palate at rates ranging from 9% to 100% across studies, depending on when the scan was performed and the screening protocol used. Isolated cleft palate, however, was detected at rates from 0% to just 22% with 2D imaging. Three-dimensional ultrasound in high-risk women performed considerably better, picking up cleft lip at about 100% and cleft palate at rates up to 89%, though results varied.
30PubMed. Diagnostic accuracy of transabdominal ultrasound in detecting prenatal cleft lip and palate: a systematic reviewCombining 2D and 3D ultrasound improves accuracy, but cleft palate diagnosis remains more error-prone than cleft lip detection because the palate is hidden behind other structures in the fetal face.
31PubMed Central. Accuracy of Prenatal Ultrasound Scans for Screening Cleft Lip and Palate: A Systematic ReviewFertility Treatments and Cleft Risk
Parents who conceive through IVF or related procedures sometimes worry about birth defect risks. For orofacial clefts specifically, the evidence is reassuring. A meta-analysis of cohort studies looking at multiple pregnancies achieved through IVF or ICSI found that the rate of cleft lip and palate was similar between these pregnancies and those conceived without assistance.
32PubMed. Multiple pregnancies achieved with IVF/ICSI and risk of specific congenital malformations: a meta-analysis of cohort studiesA separate meta-analysis comparing ICSI specifically with other IVF methods found no significantly increased risk for oral clefts.
33International Journal of Epidemiology. Birth defects in children conceived by ICSI compared with children conceived by other IVF-methods; a meta-analysis