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 The chemical, a dye called gadolinium contrast media, is used in
about 30% to 45% of MRI scans in the U.S. to help enhance
differences in internal organs, soft tissues, blood vessels, and
bones.
"It is known that gadolinium contrast crosses the placenta and
enters fetal circulation," said lead study author Steven Bird of the
Food and Drug Administration's Center for Drug Evaluation and
Research in Silver Spring, Maryland.
The safety of gadolinium-based contrast agents, or GBCAs, in
pregnant women "has not been established, and their use during
pregnancy is not recommended unless essential to the health of the
woman or fetus," Bird told Reuters Health by email. "Available data
from cohort studies and case reports have revealed inconsistent
findings regarding the association between GBCAs and adverse fetal
outcomes."
Bird and colleagues used the FDA-funded Sentinel Distributed
Database to analyze data from nearly 4.7 million pregnancies in that
resulted in live births between 2006 and 2017. They looked for the
prevalence of MRI procedures with and without GBCAs among pregnant
women, including the trimester and the location of the scan on the
body.
The research team found 6,879 exposures to GBCAs in 5,457
pregnancies, representing one GBCA exam per 860 pregnancies, or
about 0.1% of all pregnancies. Half of the MRIs were scans of the
head, but 22% were for the pelvic and abdominal regions, which may
be more likely to affect the fetus.
About 70 percent of exposures in pregnant women occurred during the
first trimester, the study authors wrote in the journal Radiology.
The finding that most pregnancies with in-utero exposure to
gadolinium occurred in the first few weeks, "when a woman may not
yet be aware of her pregnancy . . . raises the importance for
patients and healthcare providers to evaluate the possibility of
pregnancy before administration of GBCA," Bird said.
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"Increased attention to pregnancy screening measures may help reduce
inadvertent exposure to gadolinium," Bird said. "Healthcare
providers should use GBCAs only when the additional diagnostic
information provided by contrast is necessary."
Bird and colleagues are collaborating on and funding a follow-up
study among pregnant women to evaluate fetal and neonatal outcomes
after GBCA exposure during pregnancy. The FDA will also continue to
monitor reports of adverse events, he said.
The American College of Radiology recommends screening women of
reproductive age for pregnancy before any MRI scan and states that
GBCAs should only be used after careful consideration that the
benefits to the mother and fetus outweigh the potential risks.
"Gadolinium-based contrast agents are increasingly being used in
magnetic resonance imaging," said Javier Lafuente of Gregorio
Maranon Hospital in Madrid, Spain. Lafuente, who wasn't involved
with this study, has researched GBCAs in MRIs.
"In general terms, these compounds are safe," he said. Nevertheless,
he added, even in patients who are not pregnant, "adverse reactions,
the possibility of nephrotoxicity from these compounds, and the
possibility of developing nephrogenic systemic fibrosis could have
contraindications for their clinical use."
SOURCE: http://bit.ly/2KIp6C2 Radiology, online August 20, 2019.
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