Abstract: Subclinical hypothyroidism （SCH） during pregnancy increases the risk of adverse pregnancy outcomes，and increases fetal neurocognitive disorders. In recent years，a lot of clinical and experimental results in field of gestational SCH were published. Some studys suggested that thyroid hormone （TH） deficiency affected the expression of the neuronal nicotinic acetylcholine receptor alpha 4 subunit. It may be one of SCH mechanisms of fetal intelligence. The fixed dose of oral thyroxine during pregnancy can better regulate the thyroid stimulating hormone（TSH） level and the iodine intake during pregnancy which is related with SCH pathophysiology. This article reviewed the research progress on the diagnostic criteria of gestational SCH，the pathological mechanism of fetal intelligence，the new therapeutic method and the iodine intake standard on pregnancy.

Key words: Pregn, Hypothyroidism, Nervous system, Thyroxine, Iodine