Use of CT scans during pregnancy soars, may pose health risk

The use of computed tomography scans during pregnancies has increased significantly over the past 21 years in the U.S. and one province in Canada.

According to a large study involving multiple sites looking into the use of advanced imaging in pregnancy, CT scans were performed in about 0.8 percent of pregnancies in the U.S. and 0.4 percent in Canada in Ontario in 2016.

While still a small percentage, those rates have increased nearly fourfold in the U.S. and doubled in Ontario over the 21 years of the study.

Results of the research were published last week in JAMA Network Open. The use of CT scans could be problematic because it exposes mothers and fetuses to ionizing radiation, which could cause negative long-term health effects.

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Researchers with the National Cancer Institute's Radiation-Induced Cancers study reviewed data from six integrated healthcare systems in the United States and Ontario. The study included 2.2 million women who had 3.5 million live births between 1996 and 2016.

They tracked the combined use of advanced medical imaging during pregnancy, including CT scans, radiography, angiography/fluoroscopy and nuclear medicine, which involve ionizing radiation. Researchers also studied the use of magnetic resonance imaging, or MRI, which does not involve ionizing radiation. Ultrasound was not included in the study.

In general, CT scans are quicker, easier and more widely available than MRIs and other advanced imaging, but they require a large dose of ionizing radiation, many times higher than the levels that are encountered during a chest X-ray.

"Most pregnant women get routine ultrasound (exams) to monitor fetal growth, which delivers no ionizing radiation," says co-lead author Diana L. Miglioretti, biostatistics professor at the University of California, Davis, Department of Public Health Sciences, and senior investigator with Kaiser Permanente Washington Health Research Institute. "But occasionally, doctors may want to use advanced imaging to detect or rule out a serious medical condition of the expectant mother, most often pulmonary embolism, brain trauma or aneurysm, or appendicitis."

Rates of CT scanning during pregnancy in the United States started leveling off in 2007 and have been trending downward since 2010, the study found. Meanwhile, overall rates continued to increase in Ontario, but during the study period, they were 33 percent lower than in the United States.

Researchers with the Radiation-Induced Cancers study now are examining the radiation doses that patients receive during medical imaging and identifying possible associations between imaging and the risk of childhood cancer.

"This study has given us a chance to look more closely at the use of advanced imaging in pregnancy," says Marilyn L. Kwan, co-lead author and senior research scientist in the Kaiser Permanente Northern California Division of Research. "It's important to quantify exposure to ionizing radiation because it can cause cancer and birth defects and should be kept to a minimum, especially during pregnancy."

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