Clubfoot develops from a combination of genetic predisposition, environmental exposures, and physical conditions inside the uterus. No single cause explains most cases. About 1 in 850 babies are born with clubfoot worldwide, making it one of the most common birth differences. In roughly 80% of cases, the condition appears on its own with no other health problems, and the exact trigger remains unknown.
Isolated vs. Syndrome-Related Clubfoot
Clubfoot falls into two broad categories, and the causes differ between them. Isolated (also called idiopathic) clubfoot is by far the more common type. The foot turns inward and downward, but the baby has no other structural differences. Syndrome-related clubfoot, on the other hand, occurs alongside conditions like spina bifida, arthrogryposis, or certain chromosomal disorders. The genes involved in each type are largely different, and so are the treatment paths. If your baby has been diagnosed with clubfoot on a prenatal ultrasound, one of the first things a specialist will look for is whether it appears isolated or connected to a broader condition.
The Genetic Component
Clubfoot runs in families, but it doesn’t follow a simple one-gene pattern. Researchers describe it as a multifactorial trait, meaning multiple genes contribute, each adding a small amount of risk. In some families, a dominant gene with incomplete penetrance appears to drive the pattern, which means you can carry the gene without developing clubfoot yourself.
The recurrence numbers give a clearer picture of how genetics plays out in practice. If one child in a family is born with clubfoot, the chance of a subsequent sibling also having it is roughly 3 to 8 percent. If both a parent and a child are affected, that risk jumps to about 10 percent in some populations and as high as 30 percent in others. These numbers vary by ethnicity. Studies of Maori families in New Zealand, for example, found substantially higher recurrence rates than those seen in European populations.
Boys are affected about twice as often as girls. In large studies, only 25 to 36 percent of clubfoot cases are female. Firstborn children also appear to be at slightly higher risk, though the reasons aren’t fully understood.
Physical Constraints in the Uterus
The developing foot can be physically pushed into an abnormal position when space inside the uterus is limited. Low amniotic fluid (oligohydramnios) is one of the clearest mechanical risk factors. Without enough fluid cushioning the baby, the feet can press against the uterine wall for extended periods during the weeks when bones and tendons are forming.
Other conditions that crowd the uterus raise similar concerns: breech presentation, carrying twins or multiples, and structural differences in the uterus itself. Amniotic band syndrome, where strands of tissue wrap around fetal limbs, can also restrict normal foot positioning. Even an amniocentesis performed before 15 weeks of gestation has been linked to increased risk, likely because of temporary changes in fluid levels at a critical stage of development.
It’s worth noting that during a routine ultrasound, a foot pressed temporarily against the uterine wall can mimic the appearance of clubfoot. Sonographers are trained to visualize the foot away from the wall before making any assessment.
Maternal Smoking and Clubfoot Risk
Smoking during pregnancy increases the odds of clubfoot by about 34 percent on its own. That number comes from a large study published in the American Journal of Epidemiology that controlled for other risk factors. While a 34 percent increase in odds sounds modest, the risk compounds when combined with a family history of clubfoot. A gene-environment interaction appears to be at play: smoking may not cause clubfoot independently in most cases, but it can tip the balance in a baby who already carries genetic susceptibility.
Gestational Diabetes
Gestational diabetes is associated with a 40 percent increase in the odds of clubfoot. The mechanism likely involves altered blood sugar levels affecting early limb development, though the exact pathway isn’t fully mapped. Pre-existing diabetes carries risk as well. Managing blood sugar throughout pregnancy matters for many aspects of fetal development, and foot formation appears to be one of them.
Do Medications Play a Role?
SSRI antidepressants taken during the first trimester have been investigated as a possible risk factor. A large Scandinavian study tracking over one million births found a slightly elevated rate of clubfoot among babies exposed to SSRIs early in pregnancy, but the increase was not statistically significant. The researchers concluded that the association was not substantiated as a true, clinically meaningful risk. For anyone weighing the decision to continue antidepressants during pregnancy, this is one concern that appears to carry less weight than initially suspected.
When Clubfoot Is Detected
Clubfoot can be spotted on ultrasound as early as 13 to 16 weeks of pregnancy, when the sonographer examines the soles of both feet. At this stage, the foot’s position relative to the leg is visible enough to flag a potential concern. A finding this early doesn’t always confirm clubfoot. Some cases resolve on their own as the baby grows and repositions, particularly those caused by temporary fetal posture rather than structural differences in bone or tendon.
If clubfoot is confirmed, the next step is usually a detailed anatomy scan to check for other structural differences. Isolated clubfoot has an excellent prognosis. The vast majority of cases are correctable after birth through a series of gentle casts applied over several weeks, often followed by a brace. Knowing the cause, whether genetic, mechanical, or both, helps the care team anticipate whether the condition is likely to respond to standard treatment or whether additional evaluation is needed.
Regional Differences in Prevalence
Clubfoot is not equally common everywhere. A systematic review covering nearly 45 million births found a global average of about 1.2 cases per 1,000 births. Southeast Asia has the highest rates at 1.8 per 1,000, followed by sub-Saharan Africa at 1.3 per 1,000. These differences likely reflect a mix of genetic variation across populations, differing rates of environmental exposures like smoking, and disparities in prenatal nutrition and healthcare access. Folic acid supplementation, widely recommended to prevent neural tube defects, may also play a protective role, as one of the genes most frequently linked to isolated clubfoot is involved in how the body processes folate.