Factor V Leiden is a genetic condition and can be inherited from a parent. It is important to understand that each person inherits two copies of every gene, one from their mother and the other copy from their father. Individuals who inherit one copy of the factor V Leiden mutation from a parent are called heterozygotes.
Heterozygotes have a 50% chance with each pregnancy of passing the mutated gene to their offspring (and therefore they also have a 50% chance of having a child who does not inherit the gene mutation). People who inherit two copies of the mutation, one from each parent, are called homozygotes
. Homozygotes will always pass one copy of the mutated gene to their offspring.
If both parents are heterozygotes (carry one factor V Leiden mutation) than they would have a 25% chance of having a child with two factor V Leiden mutations, a 25% chance of having a child with no mutations, and a 50% chance of having a child with one mutation.