Do no harm: avoidance of herbal medicines during pregnancy.

Herbal medicines are regarded by the public and some health care providers as gentle and safe, but there is no scientific basis for that belief. The active ingredients of plant extracts are chemicals that are similar to those in purified medications, and they have the same potential to cause serious adverse effects. This commentary summarizes recent data on the poor quality control and toxicity of herbal remedies and on the pharmacologic activities of ginger, which is used for treatment of morning sickness. There are no rigorous scientific studies of the safety of dietary supplements during pregnancy, and the Teratology Society has stated that it should not be assumed that they are safe for the embryo or fetus. Obstetricians should advise women not to expose their fetuses to the risks of herbal medicines.