Also known as Chinese angelica, dong quai produces many effects that are similar to black cohosh. Like black cohosh, it has mild estrogenic activity which may decrease the effectiveness of oral contraceptives. The National Institutes of Health warn that it also has anticoagulant effects, and it appears to have alter the the lining of the uterus. Additionally, dong quai can contribute to hypertension-- a common concern for women taking birth control pills. Research about dong quai is very limited, and experts are uncertain about whether it increases or decreases fertility. Until more is known, it should be avoided by women using oral contraceptives.