Sadly, the full article is behind a paywall but even the abstract is interesting.

This is highly pertinent given how hrt (esp. orals) raises clot risk in the first year of use. Note also the comments at the very end of the summary bullet points about Factor V Leiden and vitamin E. (free signup required to read)

In contrast to oral estrogen, transdermal estrogen does not confer additional risk on women who carry a prothrombotic mutation. The safety of transdermal estrogen has to be confirmed in randomized trials.

Some evidence suggests that the thrombotic risk from transdermal HRT is lower than the thrombotic risk from oral preparations, in women with and without prothrombotic mutations [Scarabin et al 2003 , Straczek et al 2005]. In one study, women with factor V Leiden who used oral estrogen had a 16-fold higher risk of VTE than non-users without the mutation. In contrast, the thrombotic risk in women with factor V Leiden who used transdermal estrogen was similar to that in women with a mutation who did not use estrogen. Among women with factor V Leiden, the use of oral estrogen was associated with a fourfold higher risk of VTE than transdermal estrogen [Straczek et al 2005]. However, there are no prospective trials confirming the safety in women with thrombophilia and/or prior VTE.