Why is medicinal use of thyme strongly advised against for pregnant women due to its traditional properties?

Thyme may act as an emmenagogue, stimulating menstrual flow or uterine contractions

While consuming thyme normally in food during pregnancy is generally considered acceptable, using it in larger, medicinal amounts is highly cautioned against, particularly because of its traditional classification as an emmenagogue. An emmenagogue is a substance capable of stimulating or increasing menstrual flow or provoking uterine contractions. This specific property presents a significant theoretical risk during pregnancy, as inducing uterine contractions could potentially lead to adverse outcomes such as miscarriage or premature labor. Given the insufficient safety data for therapeutic doses in pregnant or breastfeeding women, sticking only to culinary amounts is the strongly recommended route to avoid stimulating uterine activity.