More women are exposed to gadolinium-based contrast agents (GBCAs) in their first trimester compared to the later weeks of pregnancy, according to an Aug. 20 study published in Radiology. But some experts warn this information should not lead to drastic conclusions.
Up to 45% of MRI exams in the U.S. utilize GBCAs to improve scan quality, wrote lead author Steven Bird, PharmD, PhD, in a news release. And while gadolinium is a known toxin, the potential risks of GBCAs remain little understood.
“With regard to pregnancy, studies have shown that GBCAs pass through the placental barrier and enter the fetal circulation,” Bird, with the FDA’s Division of Epidemiology, and colleagues wrote. “Food and Drug Administration–approved labeling was updated to state that GBCA administration should be considered during pregnancy only if the imaging is essential and cannot be delayed.”
To gain a better understanding of GBCA exposure in pregnant women, Bird and colleagues retrospectively analyzed data on 4,692,744 U.S. pregnancies resulting in live births between 2006 and 2017.
The team found 5,457 births were exposed to GBCAs, equating to one in 860 pregnancies. A majority (3,499 exams) of exposures were from head MRIs; pelvic and abdominal MRI scans made up 22.3% of all contrast-enhanced MRIs during pregnancy.
More than 70% of GBCA exposures took place during the first trimester, a 4.3-fold greater prevalence compared to the second trimester and 5.1-fold greater prevalence compared with numbers in the third trimester.
“Unintended fetal exposures to gadolinium can occur during early pregnancy among women who are not yet aware they are pregnant,” Bird said in the release. “Increased attention to existing pregnancy screening measures may help reduce inadvertent exposures to gadolinium contrast.”
In an accompanying editorial, David F. Kallmes, MD, and Robert E. Watson Jr., MD, PhD, each with the Mayo Clinic in Rochester, Minn., suggested the results should serve as a “wake-up call” for clinicians to identify early pregnancies if gadolinium is being considered for an MRI exam.
“One thing is certain: There is a lot of uncertainty surrounding this topic,” the pair wrote. “…deciding to implement modifications to current pregnancy screening methods, which might cause profound problems in patient throughput, seems premature. Denying a patient medically indicated contrast material–enhanced MRI due to concerns about potential fetal exposure in the earliest stages of an unknown pregnancy, particularly when we are unaware of any definite deleterious effects, does not seem to serve the best needs of the patient.”
The FDA is continually monitoring reports of adverse events associated with gadolinium exposure in utero, according to the release. Bird et al. suggested a few ways radiology centers may avoid “inadvertent” administration of GBCA: a safety screening form asking about potential pregnancy, technologists can ask if a woman is pregnant, display signs urging women to tell radiology staff if they’re pregnant and testing when appropriate.