Blue cohosh is an attractive woodland perennial herb, native to eastern North America, which has compound leaves with a smooth, blue-green waxy surface. According to most treatments, the genus has only one species in North America and one in Asia; a recent treatment recognizes a second American species, C. giganteum, which is said to have, on average, larger leaves and flowers and a later flowering time. However, the two supposed species occur together over a broad range, often in mixed populations, and evidence for their separation is not conclusive. The attractive blue ?berries? are actually naked seeds, the fruit wall having been lost during development, that develop a fleshy outer layer. The rhizome and roots were used in Native American herbal traditions to treat a number of diseases, notably gynecological problems, and to stimulate labor, which is its primary use today. Blue cohosh is among the products most frequently used by nurse-midwives to stimulate labor.

While almost no scientific study of blue cohosh has been conducted, some potential safety risks have been brought to public attention. Side effects reported by midwives include excessively strong tetanic contractions, which could lead to cesarean section. Blue cohosh contains compounds that can be toxic in sufficient doses, and other side effects have been reported when the plant was used in an attempt to induce abortion. Isolated and concentrated compounds from blue cohosh were found in one study to be teratogenic or toxic in cultured rat embryo cells, but no research was done using crude blue cohosh extracts or live animals. Blue cohosh should never be taken in early pregnancy in any case because of the possibility that it might induce a miscarriage; however, it should be emphasized that the plant is neither safe nor reliable for intentional use as an abortifacient. Two case reports in medical literature link use of blue cohosh with neonatal stroke or heart attack, although such anecdotal reports do not prove causality, just as remission of a single person?s cancer following use of an herbal product does not prove that the product is a cancer cure. Most infants exposed to blue cohosh as a labor stimulator do not suffer any ill effects. However, the existing information provides some cause for concern, and more research would be desirable.

Selected References

Hannan, G.L., and H. A. Prucher. 1996. Reproductive biology of Caulophyllum thalictroides (Berberidaceae), an early flowering perennial of eastern North America. Amer. Midl. Nat. 136:267-277.

Kennelly, E. J., T. J. Flynn, E. P. Mazzola, J. A. Roach, T. G. McCloud, D. E. Danford, and J. M. Betz. 1999. Detecting potential teratogenic alkaloids from blue cohosh rhizomes using an in vitro rat embryo culture. J. Nat. Prod. 62:1385-1389.

Loconte, H. 1997. Caulophyllum. Pp. 274-275 in: Flora of North America Editorial Committee, eds., Flora of North America, vol. 3. Oxford University Press: New York.

Loconte, H., and W. H. Blackwell. 1981. A new species of blue cohosh (Caulophyllum, Berberidaceae) in Eastern North America. Phytologia 49:483.

Loconte, H., and W. H. Blackwell. 1985. Intrageneric taxonomy of Caulophyllum (Berberidaceae). Rhodora 87:463-469.

McFarlin, B. L., M. H. Gibson, J. O?Rear, and P. Harman. 1999. A national survey of herbal preparation use by nurse-midwives for labor stimulation. Review of the literature and recommendations for practice. J. Nurse Midwifery 44:205-216.

Rao, R. B., and R. S. Hoffman. 2002. Nicotinic toxicity from tincture of blue cohosh (Caulophyllum thalictroides) used as an abortifacient. Vet. Hum. Toxicol. 44:221-222.