quality:corruption, structural:scholar_edition, linguistic:translation, structural:expansion
Birth defect investigations

While during the preimplantation period, that is one to ten days following conception, intrauterine radiation exposure of "at least 0.2 Gy " can cause complications of implantation and death of the human embryo. The number of miscarriages caused by the radiation from the bombings, during this radiosensitive period, is not known.

One of the early studies conducted by the ABCC was on the outcome of pregnancies occurring in Hiroshima and Nagasaki, and in a control city, Kure, located 29 km (18 mi) south of Hiroshima, to discern the conditions and outcomes related to radiation exposure. James V. Neel led the study which found that the overall number of birth defects was not significantly higher among the children of survivors who were pregnant at the time of the bombings. He also studied the longevity of the children who survived the bombings of Hiroshima and Nagasaki, reporting that between 90 and 95 percent were still living 50 years later.

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.

In 1985, Johns Hopkins University geneticist James F. Crow examined Neel's research and confirmed that the number of birth defects was not significantly higher in Hiroshima and Nagasaki. Many members of the ABCC and its successor Radiation Effects Research Foundation (RERF) were still looking for possible birth defects among the survivors decades later, but found no evidence that they were significantly common among the survivors or inherited in the children of survivors.