Abstract
It is well established that maternal hypothyroidism has adverse effect on fetal development. Our goal is to decrease the adverse effect both on mother and fetus by screening thyroid function before pregnancy and treating hypothyroidism or subclinical hypothyroidism as early as possible. We discuss hypothyroidism and subclinical hypothyroidism from the diagnosis by using TSH, free T4, total F4, and free T4 index to the timely and dosage of treatment.