Exposing an unborn child to x-rays more than doubles the chance that the child will contract cancer before reaching adulthood, according to a report published in the New England Journal of Medicine on February 27.


An unborn child “may be especially sensitive to the carcinogenic effects of ionizing radiation,” say the authors, who compared sets of twins who did and did not receive x-rays while in the womb.  Twins were studied because, until a few years ago, doctors often used x-rays to confirm that a pregnant woman was carrying twins.


The researchers identified 31 children, all born with a twin brother or sister, who developed cancer.  Research calculations showed that the unborn child exposed to x-rays is nearly 2 1/2  times more likely to develop cancer during childhood.


There is also a sevenfold increase in cancer among twins who were x-rayed before birth and whose mothers had lost a previous child, either through abortion or stillbirth.