All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
First of all, it should be mentioned that it is not permissible to swallow the blood which comes out of one's mouth or gum if one is able to spit it out, because it is considered among the impure blood according to the view of the majority of the scholars .
As regards whether or not it breaks the fast if one swallows it, then please refer to Fatwa 89979.Allaah Knows best.