Thromboembolism remains the major cause of maternal mortality in the United Kingdom. There are important differences in the diagnosis and treatment of thrombosis in pregnant patients compared with the non-pregnant patient. Thromboprophylaxis should be considered for high-risk women (for example those who had previously experienced thrombosis). For women in high-risk obstetric situations (for example those who had experienced Caesarean section). Inherited and acquired thrombophilias increase the risk of thrombotic episodes during pregnancy, and may play a role in adverse obstetric events.