The relationship of supplemental iodine to neural tube defects in Rochester, New York, 1924-1932.

The geographic distribution of infants born with anencephaly and spina bifida in Rochester, New York, in 1924-1932, was examined to test the hypothesis that iodine supplemented water may have reduced the prevalence of these defects. During this period the region had a high prevalence of iodine deficiencies. Comparing the prevalence of neural tube defects in an area with iodine supplemented water to one without iodine supplementation, we found no significant difference in prevalence at birth of neural tube defects. Because the prevalence rates for these defects in children of foreign-born parents (except the Irish) was low, we reexamined the data, excluding these cases. There remained no differences in rates. Iodine supplemented water thus appears to have had no effect on the occurrence of neural tube defects.