Why Does Clubfoot Happen? Causes Explained Simply
When your baby is diagnosed with clubfoot, one of the first questions that springs to mind is: why does clubfoot happen? It's a question that deserves an honest, clear answer. The truth is that for most babies — around 80% — the exact cause is unknown. This type is called idiopathic clubfoot, and while that might sound frustrating, it actually means that the condition isn't caused by anything you did or didn't do during pregnancy.
This article explains what we currently know about what causes clubfoot, what the latest research tells us, and — perhaps most importantly — what doesn't cause it. Whether your baby has just been diagnosed or you're researching during pregnancy after a prenatal scan, this guide is written to provide reassurance alongside the facts.
The Simple Explanation
Clubfoot happens when the muscles, tendons, and ligaments on one side of the foot and ankle are tighter and shorter than they should be, pulling the foot into an abnormal position. Specifically:
- The Achilles tendon is too tight, pulling the foot downwards (equinus)
- The inner ligaments and tendons are too tight, pulling the foot inwards (varus and adduction)
- The bones in the foot are positioned abnormally, held in place by the tight soft tissues
This all happens during the first trimester of pregnancy, when the baby's feet are developing. By the time the foot is fully formed (around weeks 12-14 of pregnancy), the abnormal position is established. For more on timing, see when clubfoot develops in pregnancy.
Idiopathic Clubfoot: The Unknown Cause
In roughly 80% of cases, clubfoot is classified as idiopathic — a medical term that means the cause is unknown. This is the most common type and generally has the best treatment outcomes with the Ponseti method.
While the word "unknown" can be unsettling, it's important to understand what it means in practice:
- It does NOT mean doctors are baffled or that something mysterious is wrong
- It DOES mean that no single gene, no single environmental exposure, and no specific event during pregnancy has been identified as "the" cause
- Current research strongly suggests that idiopathic clubfoot results from a combination of multiple genetic and environmental factors acting together — a concept known as multifactorial inheritance
Genetic Factors
There is strong evidence that genetics plays a role in clubfoot. Here's what the research shows:
Family History
Clubfoot runs in families to some degree:
- If one parent had clubfoot, the chance of their child having it is approximately 3-4% (compared with 0.1% in the general population)
- If a sibling has clubfoot, the chance for the next child is approximately 2-5%
- If both a parent and a sibling are affected, the risk rises further
For a detailed exploration, see our guide on whether clubfoot is genetic or hereditary.
Twin Studies
Twin studies provide powerful evidence for a genetic contribution:
- Identical twins: If one twin has clubfoot, the other has approximately a 33% chance of also having it
- Non-identical twins: The concordance drops to approximately 3%
- This difference strongly suggests a genetic component, but the fact that identical twins aren't 100% concordant also shows that genetics isn't the whole story
Specific Genes
Researchers have identified several genes that appear to be involved:
- PITX1: A transcription factor gene crucial for lower limb development. Variations near this gene are the most consistently replicated genetic association with clubfoot
- TBX4: Another gene involved in limb development
- Muscle development genes: Genes involved in the formation of muscles and connective tissue in the lower limbs
- Collagen genes: Some studies have linked variations in collagen-related genes to clubfoot risk
Importantly, no single gene causes clubfoot on its own. It's the combination of many small genetic effects that contributes to overall risk.
Environmental Factors
Several environmental factors during pregnancy have been associated with an increased risk of clubfoot:
Smoking
Maternal smoking during pregnancy is one of the most consistently identified risk factors. Studies suggest that smoking increases the risk of clubfoot by approximately 20-30%. The mechanism may involve reduced blood flow to the developing limbs or direct toxic effects on muscle and connective tissue.
Amniotic Fluid Levels
Oligohydramnios (low amniotic fluid) has been associated with an increased risk of clubfoot, possibly because reduced fluid restricts foetal movement and allows the feet to become compressed into abnormal positions. However, most babies with clubfoot have normal amniotic fluid levels.
Seasonal Variation
Some studies have found slight seasonal patterns in clubfoot incidence, which could suggest environmental factors that vary with season (such as viral infections, vitamin D levels, or temperature). However, these findings are inconsistent and may not apply to all populations.
Other Factors
Research has also explored links to:
- Selective serotonin reuptake inhibitors (SSRIs): Some studies suggest a small increased risk with early pregnancy SSRI use, though findings are conflicting
- Recreational drug use: Some association has been reported, particularly with cannabis
- Maternal diabetes: A weak association has been suggested in some studies
- Maternal age: Some studies show slightly higher risk in very young or older mothers
Syndromic Clubfoot: When There Is an Identified Cause
In approximately 20% of cases, clubfoot occurs as part of a broader condition or syndrome. This is called syndromic or secondary clubfoot. Common underlying conditions include:
- Spina bifida and neural tube defects: Disrupted nerve supply to the feet can cause clubfoot
- Arthrogryposis: A condition causing multiple joint contractures throughout the body
- Chromosomal conditions: Such as trisomy 18 (Edwards syndrome)
- Congenital myotonic dystrophy: An inherited muscle condition
- Amniotic band syndrome: Fibrous bands in the amniotic sac that can compress developing limbs
See our comprehensive guide on clubfoot-associated conditions for more detail.
What Does NOT Cause Clubfoot
Just as important as understanding what causes clubfoot is knowing what doesn't cause it:
- It's NOT caused by anything you ate or drank (other than alcohol in excess, which can cause a range of foetal abnormalities)
- It's NOT caused by exercise, stress, or work during pregnancy
- It's NOT caused by the baby's position in the womb — that's a different condition called positional talipes, which is much milder and self-correcting
- It's NOT caused by wearing certain shoes or walking a certain way during pregnancy
- It's NOT caused by "bad luck" — it's a biological variation that occurs during early foetal development
The Gender Factor
Clubfoot is approximately twice as common in boys as in girls. This sex difference is thought to relate to differences in developmental thresholds, hormonal influences, and genetic susceptibility. For more detail, see our article on why clubfoot is more common in boys.
Current Research
Research into the causes of clubfoot is ongoing. Key areas include:
- Genome-wide association studies (GWAS): Large-scale genetic studies to identify additional genes involved
- Epigenetics: How environmental factors modify gene expression during development
- Developmental biology: Understanding the precise mechanisms of foot formation during the first trimester
- Prevention: While no preventive strategies exist yet, a better understanding of causes could eventually lead to them
Frequently Asked Questions
Q: Is clubfoot caused by something I did during pregnancy?
A: No. In the vast majority of cases, clubfoot is NOT caused by anything you did. It's a developmental variation that occurs during the first trimester and is thought to result from a combination of genetic and environmental factors that are largely beyond anyone's control. Please don't blame yourself.
Q: If I have a family history of clubfoot, will my baby have it?
A: Having a family history increases the risk, but the absolute risk remains low. Even with one affected parent, the chance of a child having clubfoot is approximately 3-4%. The vast majority of children born to parents with a family history of clubfoot will not have the condition. See is clubfoot genetic?
Q: Can clubfoot be prevented?
A: Currently, there is no known way to prevent clubfoot. However, avoiding smoking during pregnancy and maintaining good prenatal care may reduce some risk factors. The focus in the UK is on early detection (via the 20-week scan) and effective treatment with the Ponseti method.
Q: Why do some babies have clubfoot in both feet?
A: Approximately 50% of clubfoot cases are bilateral (both feet). This may reflect a higher overall genetic susceptibility or the involvement of systemic factors that affect both feet equally. Read more in our guide on what causes bilateral clubfoot.
Q: Does the cause of clubfoot affect how well treatment works?
A: Yes, somewhat. Idiopathic clubfoot (no known cause, 80% of cases) generally responds very well to the Ponseti method, with success rates above 95%. Syndromic clubfoot (associated with other conditions) may be more resistant to treatment and may require additional interventions. However, the Ponseti method is still the first-line treatment for all types.
Q: Will my next baby have clubfoot if this one does?
A: The risk for a subsequent child is approximately 2-5% if you have one child with clubfoot. While this is higher than the general population risk (0.1%), it means there is still a greater than 95% chance that your next child will not have clubfoot. Genetic counselling is available if you have concerns about future pregnancies.
For practical next steps, see Why Does Talipes Happen? What Parents Need to Know.