Hi, Welcome to HCM, I have read your query, thyroid hormones are critical for development of the fetal and neonatal brain, as well as for many other aspects of pregnancy and fetal growth. Hypothyroidism in either the mother or fetus frequently results in fetal disease; in humans, this includes a high incidence of mental retardation. The deleterious effects of thyroid dysfunction can also extend beyond pregnancy and delivery to affect neurointellectual development in the early life of the child. Demand for thyroid hormones is increased during pregnancy which may cause a previously unnoticed thyroid disorder to worsen. Thyroid hormone concentrations in blood are increased in pregnancy, partly due to the high levels of oestrogen and due to the weak thyroid stimulating effects of human chorionic gonadotropin (hCG) that acts like TSH. Thyroxine (T4) levels rise from about 6–12 weeks, and peak by mid-gestation; reverse changes are seen with TSH. Thyroxine requirements may increase in late gestation and return to pre-pregnancy levels in the majority of women on delivery. Hence, if the levels are normalised and if advised by the clinician it can be stopped. Thanks