F5 and Rare hereditary thrombophilia: Similarly, the advice for those with hereditary thrombophilia such as the Factor V Leiden and Prothrombin gene mutations, is to consider HRT containing transdermal estradiol as this is unlikely to increase the risk of VTE/ATE above background risk.5,9 Whilst testing for thrombophilia is only advised on a selective basis in those with risk factors such as family history, a positive result would trigger a consultation with a haematologist and the advice is that HRT containing transdermal estradiol is unlikely to increase their VTE risk above their own background risk.3