Pregnant women will be tested for thyroid function during their normal maternity checkups. If the level of free thyroid hormone is low, there are two types of cases: First, the thyrotropin level is normal, but the level of free thyroid hormone alone is low, and drug intervention therapy is not recommended in the current national and international guidelines. However, there is no criterion for intervention with eugenol, and regular review is sufficient. Second, low free thyroid hormone level, accompanied by elevated thyroid stimulating hormone level, indicates that the demand for thyroid hormone by the body and the fetus has increased significantly, and it can no longer meet the needs of the fetus, then oral eugenol is needed for replacement therapy.