Arnica Montana is a herb that is believed to be useful in relieving pain caused by bruises, sore throat, surgery and osteoarthritis. It’s flower is used in medicine. It is also used for topical treatment or as part of homeopathic medicine. However, the Food and Drug Administration has classified Arnica as a poisonous plant. It is not safe for pregnant women or anybody else to consume arnica as a medicine.
Arnica is used in food to add flavour to beverages, desserts and baked goods. However if taken in medicinal quantities Arnica plays the role of uterine stimulant, causing contractions in a pregnant woman leading to miscarriage or preterm labour. When applied topically for bruises, sprains, muscle and joint pain, inflammation or swelling, arnica is known to cause skin irritation including burning, blistering, rashes and other skin irritations. When taken by mouth other than as a homeopathic medicine, arnica can cause low blood pressure, dizziness, elevated heartbeat, tremors, shortness of breath, gastric disturbance, even coma and death.
Therefore it is best to avoid arnica during pregnancy.