The main reason for the increased risk of thromboembolism in pregnancy is hypercoagulability, which has likely evolved to protect women from the bleeding challenges of miscarriage and childbirth. Women are at a 4-to 5-fold increased risk of thromboembolism during pregnancy and the postpartum period compared with when they are not pregnant. Risk factors include a history of thrombosis, inherited and acquired thrombophilia, maternal age greater than 35, certain medical conditions, and various complications of pregnancy and childbirth. In this report, a case of a 25-year-old woman diagnosed with deep vein thrombosis in the fourth week of the postpartum period is presented. After the investigating the reasons of deep vein thrombosis, heterozygote factor V Leiden mutation and heterozygote activated protein c resistance were detected. This case is presented in order to emphasize that hereditary risk factors must be investigated, especially in young patients, although the patient already had an acquired risk factor such as pregnancy. (JAREM 2015; 5: 28-30)