Pregnant Women Exposed to More Risky CT Scans.

WEDNESDAY, July 24, 2019 (HealthDay News) -- Use of risky CT scans during pregnancy has risen significantly in North America in the past two decades, a new study finds.

"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," said co-lead author Marilyn Kwan. She's a senior research scientist at Kaiser Permanente Northern California division of research.

"This study has given us a chance to look more closely at the use of advanced imaging in pregnancy," Kwan added in a Kaiser news release.

While CT scans are quicker, easier and more widely available than MRIs and other advanced imaging, they have a large dose of ionizing radiation, many times higher than a chest X-ray, Kwan and her colleagues noted.

For the study, the research team analyzed data from six health care systems in the United States and the province of Ontario in Canada. The investigators assessed the use of advanced medical imaging in 2.2 million women who had 3.5 million live births between 1996 and 2016.

Over those 21 years, rates of CT use during pregnancy nearly quadrupled in the United States and they doubled in Ontario. In 2016, CT scans were performed in about 0.8% of U.S. pregnancies and 0.4% of pregnancies in Ontario.

U.S. rates started leveling off in 2007 and have declined since then, but rates continued to rise in Ontario, according to the study published online July 24 in JAMA Network Open.

Study co-lead author Diana Miglioretti, a biostatistics professor at the University of California, Davis, pointed out that "most pregnant women get routine ultrasound to monitor fetal growth, which delivers no ionizing radiation."

But, she added, "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."

Other types of advanced medical imaging are radiography, angiography/fluoroscopy and nuclear medicine, all of which involve ionizing radiation, and magnetic resonance imaging (MRI), which does not.

Another study is examining radiation doses patients are exposed to during medical imaging and possible links between imaging and the risk of childhood cancer.

Study senior author Dr. Rebecca Smith-Bindman said, "Always, but especially if you're pregnant, you should ask whether it is really medically necessary to have any imaging test that involves ionizing radiation." She's a radiology professor at the University of California, San Francisco.

"If advanced imaging is needed, ask your doctor if you can have another imaging test that doesn't involve exposure to ionizing radiation, such as MRI or ultrasound," she advised.

The U.S. National Cancer Institute and Ontario Ministry of Health provided funding for the study.

More information

The March of Dimes has more on radiation and pregnancy.