If you are pregnant, DO NOT USE any of the following herbs for any reason. Many can cause early contractions, birth defects, and even miscarriage. Make sure you check and see what herbs food and drinks contain before ingesting them. Check with your doctor or an herbalist if possible as well.
Angelica
Belladonna
Burdock
Cinnamon essential oil
Cow Parsnip
Hyssop
Immortal
Mistletoe
Motherwort
Oshá
Pennyroyal
Peony
Rue
San qi
Shepherd's Purse
Thyme oil
Vervain
Wood Betony
Wormwood
Yarrow
Yerba
And now, herbs that EVERYONE should be leary of. Some can be used in small doses. Note that if you are allergic to any herb regardless of whether it is on this list, avoid it.
Angelica
Belladonna
Chaparral
Comfrey
Datura
Germander
Hellebore
Hemlock
Henbane
Jin Bu Huan
Lobelia
Ma huang