Large, Multi-Center Study Assesses the Amount of Advanced Imaging Occurring During Pregnancy

The use of medical imaging in the United States has increased a lot over the last two decades, and imaging rates during pregnancy have not been quantified in a large, multisite setting… until now. A retrospective cohort study was performed at six integrated health care systems in the United States and Ontario, Canada, over the course of a 21-year period. Researchers analyzed 3.5 million pregnancies and reviewed the use of advanced imaging including computed tomography (CT), magnetic resonance imaging (MRI), conventional radiography, angiography and nuclear medicine. They found that during this period from 1996 to 2016, CT rates increased four-fold in the United States and doubled in Ontario, Canada. Findings were recently published in JAMA Network Open.

During pregnancy, most women receive routine ultrasounds (delivering no ionizing radiation) that monitor fetal growth. However, doctors may want to use advanced imaging methods such as CT to detect or rule out any serious medical conditions of the mother including pulmonary embolism, bleeding in the brain from trauma or aneurysm, or acute appendicitis.

"There's a tradeoff," UCSF's Rebecca Smith-Bindman, MD tells UCSF News, "CT scans provide the clearest images, they can be done quickly, and are more widely available than MRI and for some indications are the best imaging test to use . However, CT scans use ionizing radiation – a known carcinogen - and they are commonly done in areas that will exposure the fetus to the radiation."  

Dr. Smith-Bindman then goes on to say that pregnant women should always ask whether it is really necessary to have imaging tests done that involve radiation, or if the clinical question can be answered with ultrasound or MRI which do not expose the fetus to radiation. Researchers involved in this study suggest that alternative methods that do not use radiation should always be considered first to avoid unnecessary risks of exposure of women and fetuses.

Overall, the authors found that professional organizations do not consistently recommend minimizing medical imaging during pregnancy. They also found that the use of MRI, which does not use ionizing radiation, is on the rise in both countries. They concluded that it is very important to continue to monitor imaging rates in pregnant women to avoid both unnecessary testing and unnecessary ionization radiation exposure.  

Dr. Smith-Bindman, a professor-in-residence of Radiology, Epidemiology and Biostatistics, and of Obstetrics, Gynecology and Reproductive Medicine was the senior author on this study. Other authors from UCSF Radiology include Prachi Chavan, academic coordinator at the Radiology Outcomes Research Laboratory (RORL). Diana L. Miglioretti, PhD, biostatistics professor at the UC Davis Department of Public Health Sciences and senior investigator with Kaiser Permanente Washington Health Research and Marilyn L. Kwan senior research scientist in the Kaiser Permanente Northern California Division of Research were co-lead authors.

Read more in UCSF News.