One of the first questions parents ask when their baby is diagnosed with talipes equinovarus is: clubfoot what causes it? It is a natural response — you want to understand why this happened, whether you could have prevented it, and whether it might affect future pregnancies. The honest answer is that in the majority of cases, no single cause is responsible. Clubfoot arises from a combination of genetic, developmental, and environmental factors, and in roughly 80% of cases, it occurs in otherwise healthy babies with no identifiable trigger.
This article provides a thorough explanation of what current medical science knows — and does not know — about why clubfoot develops. We cover the genetics, the embryological process, the environmental contributors, and the associated conditions that may increase risk.
The Short Answer
For the majority of babies born with clubfoot, the cause falls into one of three categories:
- Idiopathic clubfoot (80%): No identifiable cause. The foot simply develops abnormally during the first trimester, likely due to a combination of genetic predisposition and chance developmental variation. This is by far the most common scenario
- Syndromic clubfoot (approximately 15-20%): The clubfoot occurs as part of a wider condition — a genetic syndrome, chromosomal anomaly, or neuromuscular disorder
- Positional factors (small minority): In rare cases, physical constraint in the womb (such as very low amniotic fluid) may contribute to foot positioning, though this is more commonly associated with positional talipes than true structural clubfoot
How the Foot Develops in the Womb
To understand what goes wrong in clubfoot, it helps to know how the foot normally forms. Human feet develop between approximately weeks 4 and 12 of pregnancy. The process is extraordinarily complex:
Weeks 4-6: Limb Bud Formation
Tiny limb buds appear on the embryo. These paddle-shaped structures contain the cells that will become all the bones, muscles, tendons, ligaments, blood vessels, and nerves of the leg and foot. At this stage, specific genes — including PITX1, TBX4, and members of the HOX gene family — direct the growth and patterning of these structures.
Weeks 6-8: Foot Plate and Early Shaping
The foot plate forms at the end of the limb bud. Individual toes begin to separate through a process called apoptosis (programmed cell death) that removes the webbing between them. The bones of the foot start as cartilage models that will later ossify into bone.
Weeks 8-12: Rotation and Positioning
This is the critical period for clubfoot. During these weeks, the foot undergoes a natural rotation from its initial inward-facing position to a position perpendicular to the leg. Every baby's foot starts in what looks like a clubfoot position — turned inward — and then rotates outward during normal development.
In clubfoot, this rotation fails to complete. The foot remains fixed in the equinovarus position: the heel points down (equinus), the sole faces inward (varus), and the forefoot is adducted (turned toward the midline). The tendons, ligaments, and joint capsules on the inner and posterior aspect of the foot and ankle tighten and contract, locking the foot in this position.
By the time the pregnancy reaches 12 weeks, the clubfoot deformity is established. This is why it can sometimes be detected on ultrasound — the foot has already formed in its characteristic position well before the 20-week anomaly scan.
Genetic Factors
Genetics are the single most studied area in clubfoot causation research. While no "clubfoot gene" has been identified, the evidence for a genetic contribution is strong.
Evidence from Family Studies
Clubfoot runs in families. The statistics demonstrate a clear genetic component:
- If an identical twin has clubfoot, the other twin has a 33% chance — far higher than the 0.1% population baseline
- Non-identical twins have approximately a 3% concordance rate
- First-degree relatives (parents, siblings) of an affected person have a 2-5% risk
- Second-degree relatives have a 0.6% risk
- The risk drops toward population baseline for more distant relations
This pattern — highest risk in genetically closest relatives, decreasing with genetic distance — is the hallmark of a polygenic trait (one influenced by many genes rather than a single gene). For more detail on these inheritance patterns, see our article on whether clubfoot is genetic.
Candidate Genes
Several genes have been implicated through genome-wide association studies (GWAS) and linkage analysis:
PITX1: This gene encodes a transcription factor essential for hindlimb identity and development. Variants near PITX1 on chromosome 5 are the most consistently replicated genetic association with clubfoot. PITX1 helps determine that a limb develops as a leg rather than an arm, and subtle variations may alter foot patterning.
TBX4: Another transcription factor gene involved in hindlimb specification. Mutations in TBX4 cause a condition called small patella syndrome, which sometimes includes foot anomalies. Milder variants may contribute to isolated clubfoot risk.
Muscle contractile genes: Several studies have identified associations with genes encoding components of the muscle contractile apparatus — the molecular machinery that allows muscles to contract. Variants in these genes may lead to imbalanced muscle forces acting on the developing foot.
Connective tissue genes: Genes involved in collagen formation and extracellular matrix composition have been linked to clubfoot. Abnormalities in connective tissue could alter the elasticity of ligaments and joint capsules, affecting foot positioning.
Apoptosis pathway genes: Some evidence points to genes involved in programmed cell death, which is essential for normal limb shaping. Disrupted apoptosis could affect tissue remodelling during foot development.
Epigenetics
Beyond the DNA sequence itself, epigenetic modifications — changes in how genes are expressed without altering the underlying code — may contribute. Environmental factors like maternal smoking or nutritional deficiencies could cause epigenetic changes during pregnancy that affect limb development genes. This area is still in its early stages of research.
Environmental and Maternal Factors
While genetics loads the gun, environmental factors may pull the trigger. These influences act during pregnancy, particularly during the first trimester when the foot is forming.
Maternal Smoking
Smoking during pregnancy is the most consistently identified modifiable risk factor. Multiple large studies have found that maternal smoking increases clubfoot risk by approximately 30-50%. The mechanism likely involves nicotine reducing blood flow to the developing limb and disrupting gene expression during the critical window of foot formation.
The effect appears dose-dependent — heavier smoking correlates with higher risk. Critically, the combination of smoking and a family history of clubfoot creates a multiplicative rather than additive increase in risk.
Low Amniotic Fluid (Oligohydramnios)
When amniotic fluid levels are abnormally low, the foetus has limited space to move. Normal foetal movement is important for musculoskeletal development — kicking and flexing the feet help them develop in the correct alignment. Severe oligohydramnios can contribute to foot malpositioning, though it is more commonly associated with positional talipes (a milder, flexible deformity) than with true structural clubfoot.
Uterine Constraint
Any factor that reduces the space available for foetal movement may theoretically contribute:
- First pregnancies (the uterus is tighter in first-time mothers)
- Multiple pregnancies (twins, triplets)
- Uterine fibroids or structural anomalies
- Breech presentation (though the causal direction is debated — clubfoot may contribute to breech positioning rather than the reverse)
Nutritional Factors
Some epidemiological evidence suggests associations between clubfoot and nutritional deficiencies during early pregnancy, particularly folic acid and vitamin D. However, these associations are weak and inconsistent across studies. Taking the recommended pregnancy supplements (folic acid and vitamin D) is sensible for overall foetal health but cannot be relied upon to prevent clubfoot specifically.
Medications
Certain medications taken during early pregnancy have been investigated:
- SSRIs (selective serotonin reuptake inhibitors): Some studies report a modest association with first-trimester SSRI exposure, though the absolute risk increase is small
- Misoprostol: This drug, sometimes used for gastric ulceration or (illicitly) for pregnancy termination, has been linked to limb defects including clubfoot when taken in the first trimester
No commonly prescribed UK medication has been definitively proven to cause clubfoot. Women taking regular medication should not stop without medical advice — the risks of untreated conditions often outweigh any potential teratogenic risk.
Vascular Theory
An alternative theory proposes that clubfoot results from disruption of the blood supply to the developing foot. Studies have found that some clubfeet have abnormal vascular anatomy — specifically, absence or hypoplasia of the anterior tibial artery.
According to this theory, impaired blood flow during the critical period of foot development leads to muscle and connective tissue abnormalities that cause the foot to adopt and maintain the equinovarus position. The vascular theory could also explain why maternal smoking (which affects blood vessel development) is a risk factor.
Neuromuscular Theory
Some researchers believe clubfoot is fundamentally a neuromuscular problem. Studies of muscle biopsy specimens from clubfeet have found abnormal muscle fibre composition — an increased proportion of type 1 (slow-twitch) fibres in certain muscle groups, suggesting a nerve supply abnormality affecting muscle development.
This theory is supported by the strong association between clubfoot and neurological conditions like spina bifida and cerebral palsy, where nerve damage directly causes muscle imbalance in the foot.
The Recoil Theory
A more recent hypothesis suggests that early arrested development of the foot, followed by a "recoil" as the leg and ankle grow but the foot does not rotate normally, creates the clubfoot deformity. In this model, the foot gets stuck at an early developmental stage and is then pulled into equinovarus by the differential growth of surrounding structures.
Why It Is Not Your Fault
This is worth stating explicitly: you did not cause your baby's clubfoot. Even when risk factors like smoking are present, they increase probability — they do not determine outcome. The vast majority of women who smoke during pregnancy do not have a baby with clubfoot, and many babies with clubfoot are born to mothers with no identifiable risk factors at all.
Clubfoot is a common developmental variation that has been documented throughout human history, across all ethnicities and social classes. It occurs in approximately 1 in 1,000 births regardless of socioeconomic factors. It is not caused by anything you ate, anything you did, or anything you failed to do.
Implications for Treatment
Understanding the cause of clubfoot is primarily a matter of scientific curiosity and recurrence risk counselling. Regardless of the underlying cause, the treatment is the same: the Ponseti method of serial casting followed by bracing. This treatment works effectively whether the clubfoot is idiopathic, syndromic, or secondary to any other cause.
Syndromic clubfoot (associated with other conditions) may have a higher relapse rate and can be more resistant to initial correction, but the Ponseti method remains the first-line approach worldwide.
Frequently Asked Questions
Q: Is clubfoot caused by something the mother did during pregnancy?
A: No. While certain maternal factors like smoking modestly increase risk, the majority of clubfoot cases occur in pregnancies with no identifiable risk factors. Clubfoot is a developmental variation — it is not caused by exercise, diet, stress, working, or any normal activity during pregnancy.
Q: Is clubfoot inherited?
A: There is a genetic component, but clubfoot does not follow a simple inheritance pattern. Having a family history increases risk, but most children with clubfoot are born to families with no prior history. It is a complex trait influenced by multiple genes and environmental factors acting together.
Q: Can clubfoot be prevented?
A: There is no guaranteed way to prevent clubfoot. Stopping smoking, taking recommended pregnancy supplements, and maintaining general health are sensible steps that may reduce risk marginally, but most cases cannot be predicted or prevented. The focus should be on early detection and prompt treatment, which has excellent outcomes.
Q: Does the cause affect how well treatment works?
A: For idiopathic clubfoot (the most common type), the Ponseti method has success rates above 95%. Clubfoot associated with neuromuscular conditions or genetic syndromes may be more difficult to treat and has a higher relapse rate, but the Ponseti method is still the recommended first approach.
Q: Will my next baby have clubfoot if this one does?
A: The recurrence risk for siblings depends on family history. If one child has idiopathic clubfoot and there is no other family history, the risk for a subsequent child is approximately 2-5%. If a parent also has clubfoot, the risk is higher — around 10-15%. Genetic counselling can provide personalised risk estimates for your family. Our article on second child risk explores this further.
Q: Is bilateral clubfoot caused by something different than unilateral?
A: Both bilateral (both feet) and unilateral (one foot) clubfoot are thought to share the same underlying causes. Bilateral clubfoot may indicate a slightly stronger genetic predisposition, but the distinction does not change treatment or prognosis. For more, see our guide to bilateral versus unilateral clubfoot.
Q: My baby has clubfoot and no other anomalies were found on scans. Is further testing needed?
A: For isolated clubfoot (clubfoot with no other detected anomalies), further genetic testing is not routinely recommended. The baby will be examined at birth by a paediatrician who will check for any other conditions. If isolated idiopathic clubfoot is confirmed, treatment with the Ponseti method can begin without delay.