Pregnancy is associated with physiological changes in thyroid function that may result in thyroid insufficiency, especially in presence of autoimmunity or iodine deficiency. Gestational hypothyroidism has been associated with adverse health outcomes for both the mother and child, including increased miscarriage risk and delayed neuropsychological development in neonate and child. The severity of such complications mainly depends on the precocity and the adequacy of L-thyroxin treatment. There is no consensus regarding systematic thyroid function testing in pregnant women. But, the majority of authors are favorable for systematic screening, especially in iodine deficient or marginally sufficient areas. However, when systematic screening could not be performed for economic reasons, physicians should achieve aggressive case finding for thyroid disease during pregnancy.