Pregnancy is a special time in woman's life. During this period her body is going trough a number of changes to accommodate the growth and the development of the fetus. The resulting changes in the body alter the pharmacokinetics of both drugs and herbal preparations. The most risky period of the first trimester of pregnancy is during organogenesis. Herbal medicines applied in that period can cause birth defects, developmental defects or delayed development of the child. A multinacional reasearch has shown that a third of pregnant woman used at least one herbal supplement during pregnancy, It is worring that the information about plants are lacking and herbal preparations are generally not standardized. Also, because the studies are mainly conducted in vitro or in vivo on animal, but only a small number on people, while for a smaller number of plants there is data obtained by conducting research on pregnant woman. For these reasons pregnant woman should avoid herbal products because there is still not enough information about their effects on the fetus and the pregnant woman. Another reason for this conclusion is that herbal remedies do not have fully known composition or uniform active substances and because of poor control (possible adulteration).