Endemic cretinism, caused by severe iodine deficiency during pregnancy, is a major cause of mental retardation in some parts of the world. Despite iodine supplementation programs, endemic cretinism is still found in southern and eastern Europe and is common in Asia, Africa, and Latin America; the prevalence may be as high as 10% in some communities. In 1990, the World Health Organization estimated that 20 million people in the world had preventable brain damage due to the effects of iodine deficiency on fetal brain development.
Endemic cretinism can be prevented by iodine supplementation before conception. Previous studies have not established, however, whether supplementation during pregnancy or in early childhood would be of value in reducing the risk.
In a new study conducted in a severely iodine-deficient area of the Xinjiang region of China, iodine was administered to women in various stages of pregnancy and to children from birth to age three years. The treated children and offspring of treated women were followed for two years. Three independent measures of neural development were assessed.
Iodine supplementation during the second trimester of pregnancy was clearly beneficial in reducing the prevalence of moderate and severe neurologic abnormalities. Iodine supplementation during the first trimester may have been effective as well, but difficulties in administering the required dose to this group of women prevented definitive conclusions from being reached. Iodine administration during the third trimester or after birth was less valuable; it did not improve neurologic status, but head growth and developmental quotients improved slightly.
These findings indicate that supplementation with iodine before the end of the second trimester of pregnancy can protect the fetal brain from the effects of iodine deficiency. "It is obviously preferable to start providing iodine before pregnancy and to provide it continuously." However, supplementation during early pregnancy would be of value in instances where adequate iodine intake cannot be ensured before conception.
Cao Xue-Yi, Jiang Xin-Min, Dou Zhi-Hong et al, Timing of Vulnerability of the Brain to Iodine Deficiency in Endemic Cretinism, New England J Medicine 331(26):1739-1744 (29 Dec 1994) [Reprints: G Robert DeLong, MD, Division of Pediatric Neurology, Duke University Medical Center, Box 3936, Durham NC 277101
Basil S Hetzel, Iodine Deficiency and Fetal Brain Damage [Editorial], New England J Medicine 331(26):1770-1771 (29 Dec 1994) [Correspondence: Basil S Hetzel, MD, International Council for Control of Iodine Deficiency Disorders, North Adelaide, SA 5006, Australia]
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