Antenatal Thyroid Screening and Childhood Cognitive Function

In this randomized trial, antenatal screening (at a median gestational age of 12 weeks 3 days) and treatment for hypothyroidism did not result in improved cognitive function in children at 3 years of age. Active secretion of thyroid hormone in the fetus does not start until about 18 to 20 weeks' gestation. 1 Studies in animals suggest that until fetal hormone secretion begins, the fetus is dependent on circulating free thyroxine (T 4 ) in the mother for growth and development, including central nervous system maturation. 1 Iodine is essential for free T 4 synthesis, and in iodine-deficient populations, an increase in cognitive performance has been observed after iodine supplementation before pregnancy. 2 – 4 High levels of thyrotropin in women during pregnancy have been associated with impaired cognitive development in their offspring. This finding suggests that antenatal . . .