Adolescent, Adult, Age Factors, Anticoagulants, Aryl Hydrocarbon Hydroxylases, Child, Child, Preschool, Cohort Studies, Cytochrome P-450 CYP2C9, Genotype, Humans, Infant, Infant, Newborn, Mixed Function Oxygenases, Phenprocoumon, Polymorphism, Genetic, Prognosis, Prospective Studies, Thrombosis, Vitamin K, Vitamin K Epoxide Reductases, Warfarin, Young Adult