EFFECTS OF ENVIRONMENTAL-FACTORS ON PERINATAL OUTCOME - NEUROLOGICAL DEVELOPMENT IN CASES OF INTRAUTERINE GROWTH-RETARDATION AND SCHOOL PERFORMANCE OF CHILDREN PERINATALLY EXPOSED TO IONIZING-RADIATION

We performed two studies to investigate environmental factors in relat ion to neurological development in infants. The first, a field study, examined the elementary school performance of 929 children who were bo rn from mothers exposed to the atomic bombing of Hiroshima, Japan, Aug ust 6,1945. The most severe mental retardation was observed in the gro up exposed between 8 and 15 weeks following fertilization, and the sec ond most severely damaged group was exposed between 16 and 25 weeks. T he second, a clinical investigation, examined infants in the perinatal center who survived intrauterine growth retardation (IUGR). Those who survived with abnormal neurological development had a mean growth arr est corresponding to a uterine height of 27 weeks of gestation. This w as at an earlier stage than those who survived with normal neurologica l development and had a mean growth arrest corresponding to 29-30 week s of gestation. A smaller head circumference at birth was closely corr elated with abnormal neurological sequelae. These results indicate tha t the brain development of the fetuses may have been affected by neuro toxic events similar to ionizing radiation. We emphasize the importanc e of avoiding neurotoxic stress to pregnant women when the fetus is in the critical period of neuronal development, before 27 weeks of gesta tional age.