Women who have to undergo a CT scan or other nuclear imaging test while pregnant can rest a little easier about the health effects: new research shows their babies are no more likely to develop cancer than other kids.
Scientists, including some from the Institute for Clinical Evaluative Sciences in Toronto, have reviewed the medical records of babies born to women who had a major radiodiagnostic test during pregnancy.
They followed the children for an average of nine years and found the rate of childhood cancers was actually lower in the kids who had been exposed to a nuclear imaging test, compared to other kids.
The rate of childhood cancer in the women who were not exposed to a test was 1.56 cancers for every 10,000 child years of follow-up. Among those kids whose mothers had had a CT scan or nuclear medicine test in pregnancy, the rate of cancer in their children was 1.13 for 10,000 child years.
The study appears in the open access journal PLoS Medicine.
Radiodiagnostic tests are sometimes needed during a woman's pregnancy to diagnose serious problems such as lung clots, appendicitis or bleeding in the brain.
Little is known about the potential effects on the fetus, and how the radiation might affect the newborn child as he or she grows older. This research should help eases the fears of mothers and their doctors about the tests.
Nevertheless, the authors say there is still some uncertainty about the relative risk of the tests.
The researchers estimated an "adjusted hazard ratio" for the risk to be 0.68, with confidence limits between 0.25 and 1.80. These confidence intervals (representing uncertainty) suggest that although the researchers did not find clear evidence for an increase in risk following imaging, they could not exclude the chance of a small increase in risk.
Given this possibility, the authors recommend that radiodiagnostic tests be performed in pregnancy only under urgent or emergency situations. Non-radiation-emitting imaging, such as MRI and ultrasounds should be considered first, they recommend.
In an accompanying commentary, Eduardo Franco and Guy-Anne Turgeon from McGill University in Montreal recommend that an international consortium be formed to pool the data on exposure-risk links from all recent research, to help shed more light on this issue.
