Thus , regardless of study design , iodine deficiency had a substantial impact on mental development .
Several review s and meta-analyses have examined the effects of iodine on mental development .
None focused on young children , so they were incomplete in summarizing the effects on this important age group .
The current systematic review therefore examined the relationship between iodine and mental development of children 5 years old and under .
The Neurologic Development of the Newborn and Young Child in Relation to Maternal Thyroid Function
A prospect i ve observational study was performed in pregnant women with known thyroid disease . We studied the effect of maternal thyroid function in the first half of pregnancy on the neurologic development of the infant in the first 2 y of life . Clinical and thyroid function data were collected from 20 pregnant women with known thyroid disease and their newborn children . Infants were divided into three groups according to their maternal thyroid function within the first half of pregnancy : Group A ( n = 7 ) : maternal sub clinical hypothyroidism , Group B ( n = 6 ) : maternal euthyroidism , and Group C ( n = 7 ) : maternal hyperthyroidism or sub clinical hyperthyroidism .  Neurophysiologic , i.e. motor nerve conduction velocity and somatosensory evoked potentials and neurologic and developmental ( Bayley scales ) assessment s were done . One infant , born to a mother with Graves ' disease , developed transient hyperthyroidism . At the age of 6 and 12 mo , the mean mental developmental index ( MDI ) score was 16 points lower for infants in Group A than for those in Group B ( p = 0.03 and 0.02 , respectively ) . At the age of 24 mo , the mean MDI score was 6 points lower , which was not statistically significant . Neurophysiologic and neurologic assessment s and the mean Psychomotor Developmental scores did not differ among the three groups . In conclusion , maternal sub clinical hypothyroidism in the first half of pregnancy was associated with a lower mean MDI score in their infants during the first year of life
Thus , regardless of study design , iodine deficiency had a substantial impact on mental development .
Several review s and meta-analyses have examined the effects of iodine on mental development .
None focused on young children , so they were incomplete in summarizing the effects on this important age group .
The current systematic review therefore examined the relationship between iodine and mental development of children 5 years old and under .