Safe Use of Herbs in Pregnancy. (Phytotherapy Review & Commentary)

The safe use of herbal medicines during pregancy is becoming an increasingly contentious issue. On the one hand, regulatory authorities appear to be adopting the policy that if there is no clear evidence of safety from controlled clinical trials, then an herb should not be recommended during pregnancy. This was well illustrated by some recent deliberations of the Complementary Medicines Evaluation Committee (CMEC) of the Australian Therapeutic Goods Administration (TGA). CMEC was assessing the safe use of over-the-counter products containing kava (Piper methysticum) and came to the conclusion, despite the lack of evidence for harm from kava during pregnancy, that kava products should carry the following warning: "Not for prolonged use. If symptoms persist seek advice from a health care practitioner. Those who are pregnant or nursing are not recommended to use Kava." The American Herbal Products Association also suggests that professional advice should be sought before using kava during pregnancy.

If this condition is applied to all commonly used herbs, then probably only ginger, which has been trialled for hyperemesis gravidarum, and senna and ginseng would not need to carry such a warning. Ironically, some herbal and scientific authors believe that these three herbs are contraindicated in pregnancy.

On the other hand, some scientists with little clinical experience in prescribing herbs have speculated about harmful effects which might ensue from the use of herbs during pregnancy. They appear to adopt the stance that even if a negative effect from an herb is only remotely possible (I would add, highly unlikely), then that herb should not be taken during pregnancy. The unspoken assumption here is that herbs are only marginally efficacious, if at all, so even the remotest risk during pregnancy is unacceptable. This approach is exemplified by the list provided in the book by Newall and co-authors. (1) According to these authors, the following innocuous herbs are contraindicated in pregnancy (their reasons are provided in parentheses):

* Agnus castus (hormonal action)

* Burdock (uterine stimulant in vivo)

* Calendula (reputed to affect menstrual cycle, uterine stimulant in vivo)

* German chamomile (reputed to affect menstrual cycle, uterine stimulant with excessive use)

* Corn silk (uterine stimulant in vitro)

* Damiana (risk of cyanide toxicity in high doses)

* Fenugreek (oxytocic, uterine stimulant in vitro)

* Gentian (reputed to affect menstrual cycle)

* Ginseng (hormonal activity)

* Hawthorn (uterine activity)

* Nettle (reputed abortifacient etc)

And so the list goes on. Much of this list was compiled by extrapolating from pharmacological experiments where the herb is injected in very high doses, or from experiments where the herb in very high concentrations is infused through isolated organs. Clearly these types of experiments are of little relevance in a careful assessment of safety.

Even some herbalists have adopted a conservative stance. In his book entitled Herb Contraindications and Drug Interactions, Francis Brinker suggests that the following relatively innocuous herbs are unsafe to take during pregnancy: alfalfa, lemon balm, basil, black pepper, burdock, calendula, catnip, chamomile, dill, fennel, fenugreek, flaxseed, garlic, gotu kola, lavender, licorice, passionflower, and St John's wort. (2) Ironically, many of...