During pregnancy various endocrine glands are in an active state and a series of physiological changes occur in all organ systems, which have direct and indirect effects on thyroid function. The effects of hypothyroidism during pregnancy on pregnancy are as follows: it can impair the neurointellectual development of the offspring and increase the risk of preterm birth, miscarriage, low birth weight, stillbirth or hypertensive disorders during pregnancy. It must be given regular treatment, which is managed as follows: once clinical hypothyroidism is identified, treatment should be started immediately and should reach the treatment goal as soon as possible, with the goal of achieving a normal range of serum TSH at all stages of pregnancy. The drug of choice should be thyroxine therapy. Women with clinical hypothyroidism who are planning to become pregnant should not become pregnant until their plasma serum is controlled to a TSH level of <2.5 mU/L. In women with clinical hypothyroidism, thyroid function should be monitored every four weeks from 1 to 12 weeks of gestation, and serum thyroid function should be checked at least once from 26 to 32 weeks of gestation.