Nigella sativa is one of the amazing traditional medicines from the middle east. Here are three studies related to clotting, prothrombin time and nigella sativa. I believe nigella sativa is not recommended during pregnancy, however. I believe that is due to the decreased clotting effect, actually.
Biol Pharm Bull 2001 Mar;24(3):307-10 Related Articles, Books
Hematological studies on black cumin oil from the seeds of Nigella sativa L.
Enomoto S, Asano R, Iwahori Y, Narui T, Okada Y, Singab AN, Okuyama T.
Department of Natural Medicine
http://evenone.com/filestore/Researc...%20Sativa_.pdfhttp://www.ncbi.nlm.nih.gov/pubmed/11256491
Effect of
Nigella sativa on blood hemostatic function in rats
http://www.sciencedirect.com/science...76d55cc8ec89d6In vitro induction of endothelial cell fibrinolytic alterations by Nigella sativa.http://www.thefreelibrary.com/In+vit.....-a0133644493
I also found these herbs which increase bleeding.
Angelica,Anise, arnica, asafetida, bromelain, chamomile, clove, danshen, devil's claw, dong quai, fenugreek, feverfew, garlic, ginger, ginkgo, ginseng, horse chestnut, licorice, meadowsweet, motherwort, onion, papain, parsley, passionflower, quassia, red clover, Reishi mushroom, rue, sweet clover, turmeric, white willow, others: increased risk of bleeding
Coenzyme Q10, green tea, St. John's wort: decreased anticoagulant effect.
I haven't researched if these herbs increase prothrombin time specifically. If so, then they could be potentially therapeutic, however, this action must be monitored for safety, especially if pregnant, there could be significant danger. The concern is that regulating coumadin is even challenging to do safely and is routinely considered, or aspirin or heparin...
Pat