Study reanalyses the data from children of atomic bomb survivors and adverse pregnancy outcomes

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The Atomic Bomb Casualty Commission (ABCC) conducted a study on the pregnancy outcomes of children of atomic bomb survivors from 1948 to 1954. This original study and subsequent other reports in 1956, 1981 and 1990 did not find significant associations of ionising radiation exposure with adverse pregnancy outcomes such as neonatal deaths, still births or congenital malformations. However, none of these previous studies included approximately 1200 induced terminations and had other outcome misclassification errors. This new analysis reconstructed and refined the data from the original ABCC study and used more advanced methods for assessing radiation doses received by the subjects and subsequent dose-response relationships. This reanalysis found that radiation is associated with an increased risk of adverse pregnancy outcomes. For fathers exposed to 0.5 – 1 Gy there was an increased risk for major malformations whilst for mothers exposed to 0.5 – 1 Gy there was an increased risk for perinatal death outcomes. However, most of the results were not statistically significant and the generalizability is uncertain due to the extreme circumstances encountered by atomic bomb survivors.

Link to study.

Congenital Malformations and Perinatal Deaths among the Children of Atomic Bomb Survivors: A Reappraisal

Comments by ARPANSA:

In Australia, the system for Radiation Protection draws on international best practice,  particularly, the International Commission on Radiological Protection (ICRP). The ICRP (ICRP, 2007) prudently recommends including the risk of heritable effects within the system of radiation protection and provides risk estimates for its application. This is further underpinned by the work of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 2001).

The findings within this study are consistent with ICRP’s approach. This study reported that ionising radiation is associated with an increased risk of adverse pregnancy outcomes, despite most of the results not finding a statistically significant association. It is likely that the lack of statistically significant associations found in both parental categories for exposure over 1 Gy is due to the small sample size for those categories. In contrast, another recent study conducted on clean-up workers from the Chernobyl nuclear accident found no evidence of heritable effects. However, the majority of participants were exposed to less than 0.5 Gy, which is below the level that the Yamada et al. study found a statistically significant association. Despite the lack of statistically significant associations found in the Yamada et al. study, the consistent increase in risk of adverse pregnancy outcomes found across the exposure groups may be useful for risk assessment purposes. This study as well as experimental observations credibly reason that the risk of heritable diseases should be included in radiation risk assessments and considered when setting exposure limits.