Although it is doubtful that mild diciency causes intellectual impairment, supplementation does prevent fetal goiter (Stagnaro-Green, 2012b). Severe diciency, on the other hand, is frequently associated with damage typically encountered with endemic cretinism (Delange, 2001). It is presumed that moderate deiciency has intermediate and variable efects. Berbel and associates (2009) began daily supplementation in more than 300 pregnant women with moderate deiciency at three time periods-4 to 6 weeks, 12 to 14 weeks, and after delivery. They found improved neurobehavioral development scores in ofspring of women supplemented with 200 ILg potassium iodide very early in pregnancy. Similarly, Velasco and coworkers (2009) found improved Bayley Psychomotor Development scores in ofspring of women supplemented with 300 ILg of iodine daily in the irst trimester. In contrast, Murcia and colleagues (2011) identified lower psychomotor scores in 1-yearold infants whose mothers reported daily supplementation of more than 150 ILg. To address this, randomized controlled trial of iodine supplementation in mildly to moderately iodinedeficient pregnant women in India and hailand is nearing completion (Pearce, 2016).
Regarding daily iodine intake, the Institute of Medicine during lactation (Chap. 9, p. 168). he Endocrine Society recommends an average iodine intake of 150 �g/d in repro ductive-aged women, and this should be increased to 250 �g during pregnancy and breastfeeding (De Groot, 2012). The of iodine be added to prenatal vitamins to achieve this average daily intake (Becker, 2006). According to Leung and coworkers (2011), however, only 51 percent of the prenatal multivitamins in the United States contain iodine. It has even been suggested that because most cases of maternal hypothyroxinemia world wide are related to relative iodine deficiency, supplementation may obviate the need to consider thyroxine treatment in such women (Gyami, 2009). However, without evidence of benefit, it is hard to justiy the cost of iodine supplementation of large numbers of pregnant women in areas with mild iodine dei ciency (Pearce, 2016).
Importantly, experts caution against oversupplementa tion. T eng and associates (2006) contend that excessive iodine intake-deined as > 300 �g/ d-may lead to subclinical hypo thyroidism and autoimmune thyroiditis. he Endocrine Soci ety, in accordance with the WHO, advises against exceeding twice the daily recommended intake of iodine, or 500 �g/ d (De
Groot, 2012; Leung, 2011).
Universal newborn screening for neonatal hypothyroidism was introduced in 1974 and is now required by law in all states (Chap. 32, p. 614). This develops in approximately 1 in 3000 newborns and is one of the most preventable causes of mental retardation (LaF ranchi, 2011). Developmental disorders of the thyroid gland such as agenesis and hypoplasia account for 80 to 90 percent of these cases. he remainder is caused by hereditary defects in thyroid hormone production (Moreno, 2008).