There are a lot of herbs that are too strong for a baby to handle (same with over the counter or prescription drugs). A lot of people have the idea that because herbs are natural they are completely safe at all times; this, however, is simply not true.
Below is a list of herbs that, due to being too strong, you should not take while you are pregnant unless your OB directly tells you to. And then,
if you must take them, take them in MODERATION.
Angelica: Can proote menstruation/miscarriage
Black Cohosh or Blue Cohosh: Can promote uterine contractions, increasing incidence of miscarriages
Coltsfoot: Contains alkaloids that may damage the liver of the fetus
Comfrey: Contains alkaloids that may damage both maternal and fetal livers
Dong Quai: Can promote menstruation/miscarriage
Echinacea: A powerful medicine that may be too concentrated for a fetus
Feverfew: Can promote menstruation/miscarriage
Ginger Root: Can promote menstruation/miscarriage (**Check with your OB as many say this is actually safe for pregnant women to take in small doses to help with morning sickness.**)
Ginseng: Can affect hormonal system during crucial stages of fetal development
Goldenseal: Can promote uterine contractions
Licorice: Can affect hormonal system during crucial stages of fetal development
Mugwort: A powerful medicine that may be too concentrated for a fetus
Pennyroyal: Can promote uterine contractions, increasing incidence of miscarriages
Red Raspberry Leaf: Can cause contractions, so should be avoided during the FIRST trimester
Tansy: Can promote menstruation/miscarriage
Valerian: A powerful medicine that may be too concentrated for a fetus
Yarrow: A powerful medicine that may be too concentrated for a fetus
Herbs to Avoid While Pregnant 
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