Abstract: Hypothyroxinemia is defined as the presence of low maternal thyroxine (T4) in the absence of thyroid-stimulating hormone (TSH) elevation,which is a kind of phenomenon of subclinical thyroid hormone deficiency.Maternal hypothyroxinemia has adverse effects on fetal neurodevelopment,such as learning,cognition,memory,motor,and the onset of neuropsychiatric diseases in progeny.We review the studies on the relationship between maternal hypothyroxinemia and fetal neurodevelopment,as well as the possible mechanisms.