Frequency of Blood Clots in Kids

Although blood clots are more common in adults, they also can occur in children. The annual incidence figures are:

  • 0.07 to 0.14 per 10,000 children

  • 5.3 per 10,000 hospital admissions

  • 24 per 10,000 neonatal intensive care unit admissions

Newborns and babies younger than one-year-old are at greatest risk for blood clots. Children in intensive care units—and those with cancers—are particularly at high risk.

A high risk of blood clots is associated with adolescence. Teenage girls have twice the rate of clots as teenage boys. This difference is related to the use of oral contraceptives and pregnancy. Even in the presence of inherited or acquired clotting risk factors, children are less likely than adults to develop clots because they generally have healthy blood vessels.


Blood clots without a known cause occur in less than 5% of children compared to approximately 40% of adults. Furthermore, most of the clotting events in children are triggered, meaning there are temporary risk factors causing the clotting disorder. Central venous catheters are a common risk factor for the development of a clotting event in children. Children with cancer, trauma or surgery, and systemic lupus erythematosus are also at increased risk of developing a clot.

Inherited conditions that may cause a blood clot in children are typically the result of missing clotting proteins that turn off clotting once it starts. Not all of these conditions have the same clotting risk. There is a greater risk of clotting with protein C, protein S, and antithrombin, while others such as the Factor V Leiden mutation or the prothrombin 20210 mutation are less important risk factors in children.