Is it safe to consume traditional medicinal plants during pregnancy?

The popularity of natural medicine is growing worldwide. Unlike conventional licensed medicines, herbal medicine practices are usually not supported by effectiveness, efficacy, or safety studies, which raise concerns about potential risks involved in their usage, particularly in high-risk patients such as pregnant women where teratogenicity is a concern. Despite a lack of science-based evidence, the use of herbal products for the management of pregnancy-associated challenges is common, due to the common notion that they are free of toxic effects and adverse reactions because they are "natural." The lack of concern about utilizing herbal remedies during pregnancy is strengthened by the lack of regulation in most countries for their marketing. However, plant-based remedies are not free of adverse reactions. Medicinal plants and herbal remedies contain substances that can be toxic to the human body and the fetus. Potential effects of indiscriminate use of medicinal plants are embryotoxicity, teratogenic, and abortifacient effects. Some plant constituents can cross the placenta and reach the fetus. Phytochemicals and their metabolites are known to induce stimulation of uterine contraction and hormone imbalance that could result in abortion. The alterations to the hormonal profile can affect conception, induce teratogenic activity, and halt the pregnancy or produce a congenital malformation. Due to the wide range of modes of action of phytochemicals, some medicinal plants may be safe to use during certain trimesters of pregnancy and harmful at other stages. This manuscript reviews available scientific information concerning potential health hazards associated with the consumption of herbal medicines during pregnancy, highlighting those herbs that should be avoided due to their potential abortifacient and/or teratogenic activity. We focused on plants that were tested by preclinical studies, and studies of these plants are summarized. Common therapeutic use of these herbs, estimated effects, toxicological effects, and animal studies of these plants is summarized. The literature reviewed suggests that consumption of the following medicinal plants should be avoided during pregnancy: Abrus precatorius, Achyranthes aspera, Ailanthus excelsa, Aloe vera, Aristolochia indica, Areca catechu, Bambusa vulgaris, Cassia occidentalis, Cicer arietinum, Cimicifuga racemose, Dolichandrone falcate, Ginkgo biloba, Hydrastis canadensis, Indigofera trifoliate, Lavandula latifolia, Maytenus ilicifolia, Momordica cymbalaria, Moringa oleifera, Musa rosacea, Oxalis corniculate, Phytolacca dodecandra, Plumeria rubra, Ricinus communis, Ruta graveolens, Stachys lavandulifolia, Senna alata, Trigonella foenum-graecum, Vitus agnus-castus, and Valeriana officinalis.