It seems that when you are pregnant and nursing, there are so few medicines or herbs that you can take, for fear that one of them might interfere with the natural process that's going on in your or your baby's body. I found this great article by Aviva Romm, M.D. on what IS safe to take, as opposed to all the things you shouldn't take or be cautious of.
5 Safe Herbs for a More Comfortable Pregnancy and Better Birth