statistically insignificant gestational age microencephaly anencephaly control group radiation National Academy of Sciences Kure Nagasaki birth defects hypocenter control Hiroshima
While the National Academy of Sciences raised the possibility that Neel's procedure did not filter the Kure population for possible radiation exposure which could bias the results, overall, a statistically insignificant increase in birth defects occurred directly after the bombings of Nagasaki and Hiroshima when the cities were taken as wholes, in terms of distance from the hypocenters. However, Neel and others noted that in approximately 50 humans who were of an early gestational age at the time of the bombing and who were all within about 1 kilometer (0.62 mi) of the hypocenter, an increase in microencephaly and anencephaly was observed upon birth, with the incidence of these two particular malformations being nearly 3 times what was to be expected when compared to the control group in Kure.
