What’s the medical plausibility of a female A-bomb victim getting pregnant one or two decades after the A-bombings (say, 1955 or 1965) and giving birth to a child who is genetically predisposed to cancer?
Or are only children who were in utero at the time of the A-bombs susceptible to cancer?
All primary oocytes are generated early in female life, unlike sperm that are continually produced. So the egg cell involved an any later pregnancy, even decades later, would have been present and could have been irradiated.
However, unlike an irradiated fully-grown human, the principal risk from irradiated gametes is not so much later cancer susceptibility in the child, but inviable embryos & miscarriages, or viable births with major birth defects of all kinds. That’s because development is a highly complex coordinated process, so even just a few defective genes can wreak havoc. In the case of relatively heavy irradiation, it would be possible to assign causation to the A-bomb irradiation if genetic analysis of (say) a deformed miscarried fetus revealed an unusually large number of DNA mutations.
But the scenario that you are describing is presumably a baby that’s basically healthy and viable, but with a genetic predisposition to cancer. This is certainly possible in principle from milder A-bomb irradiation, if by chance a few mutations just happened to hit some genes with this effect, but nothing causing other birth defects. However, even without A-bomb irradiation, any child always acquires a certain number of de novo DNA mutations anyway. So I think the problem is not that this could not happen, but that you could not unambiguously assign cause to the A-bomb radiation. All you could say is that the A-bomb radiation was a risk factor that might have caused it.
http://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(15)00209-0/fulltext?rss=yes
Take home point: We detected no association between maternal gonadal radiation exposure and risk of death caused by cancer (hazard ratio [HR] for 1 Gy change in exposure 0·891 [95% CI 0·693–1·145]; p=0·36) or risk of death caused by non-cancer diseases (0·973 [0·849–1·115]; p=0·69). Likewise, paternal exposure had no effect on deaths caused by cancer (0·815 [0·614–1·083]; p=0·14) or deaths caused by non-cancer disease (1·103 [0·979–1·241]; p=0·12).
It hasn’t been long enough to study subsequent generations.
This is still actively being researched - you can find information at the Radiation Effects Research Foundation’s website. This is the organization (formerly the Atomic Bomb Casualty Commission) that has been researching the health effects of the bombings of Hiroshima and Nagasaki on the survivors since shortly after the end of WW II.
From the FAQ on the website, the conclusion so far is:
“One of the earliest concerns in the aftermath of the atomic bombings was how radiation might affect the children of survivors. Efforts to detect genetic effects began in the late 1940s and continue. Thus far, no evidence of increased genetic effects has been found. This does not necessarily mean that no effects exist because some past studies were limited in their ability to detect genetic damage.”