A warning about using St. John's wort in conjunction with oral contraceptives Link: St. John's Wort, MS and Pregnancy - St. John's Wort Warning - St. John's Wort and Multiple Sclerosis .

For those of you using St. John's wort to treat MS-related depression, just a gentle reminder: St. John's wort can potentially interfere with the effectiveness of oral contraceptives by lowering the concentration of them in the blood. In other words, your birth control pills will not work as well if you are taking St. John's wort, and you may get pregnant.