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For most pregnant women who were exposed to gadolinium during MRI exams, this exposure occurred during the first trimester, according to the results of a longitudinal study.

The prevalence of gadolinium-based contrast agent (GBCA) exposure was 1.2 per 1,000 live births. Of the almost 7,000 GBCA exposures observed during pregnancy, 70.2% occurred during the first trimester, reported Steven Bird, PhD, PharmD, of the FDA, and colleagues, writing in .

"The number of pregnancies with in utero exposure to gadolinium was high (1 in 860), with most occurring in the first few weeks of pregnancy, when a woman may not yet be aware of her pregnancy," Bird told 番茄社区app in an email. "This raises the importance for patients and healthcare providers to evaluate the possibility of pregnancy before administration of GBCA."

GBCAs, which are used in 30% to 45% of MRI exams in the U.S., are used to provide clearer imaging and diagnostic information, according to the study authors. Although experts have not directly linked gadolinium to adverse health effects, gadolinium has been found to remain in the body after exposure.

The FDA released a safety warning in 2017 to inform consumers of the ability of gadolinium to retain in the body. During pregnancy, GBCAs cross the placental barrier and enter fetal circulation, and previous studies have linked exposure in utero to increased risk of neonatal death, stillbirth, and inflammatory skin conditions in newborns.

After an Ontario-based evaluated the potential harms of gadolinium exposure in utero, Bird said that they sought to assess gadolinium exposure patterns.

"We began looking closely into the U.S. utilization of gadolinium contrast during pregnancy in response to emerging concerns about deposition of gadolinium in the body," he noted.

Indeed, study authors found that there was approximately one GBCA exposure per 860 pregnancies, a prevalence four times greater than that observed in the Ontario-based study.

Researchers used the to identify almost 4.7 million pregnancies that resulted in a live birth. They then documented all MRI exams, performed with and without GBCAs from 2006 to 2017. Data was stratified by both location of the MRI and trimester.

Overall, there were almost 7,000 exposures in almost 5,500 pregnancies. Pregnant women were 4.3 times as likely to be exposed to GBCAs during the first trimester than the second trimester, and 5.1 times as likely during the first trimester than the third.

Most gadolinium-enhanced MRI exams were performed in the head, with headaches being the most common group of diagnostic billing codes associated with contrast-enhanced MRI. Abdominal and pelvic imaging represented 22.3% of contrast-enhanced procedures.

Susan Klugman, MD, of the Montefiore Health System in New York City, who was not involved with the research, said that she found it interesting that many exposures were in the first trimester, before pregnancy was known.

"A high percentage of the procedures were performed on the abdomen and pelvis," Klugman told 番茄社区app in an email. "I am not sure if pregnancy testing was negative prior to the procedure and if patients were counseled about the risks of exposure."

However Klugman also noted that this study was limited by its inclusion of only live births. She added that there was no information about fetal exposures, possible congenital anomalies or genetic syndromes, or patients that miscarried or elected not to continue with pregnancy.

Study authors also said that although they had information about the imaging location of the MRI, the research is limited by a lack of access to information about the reason for the MRI.

Despite these limitations, Klugman said this research informs healthcare providers about the importance of having conversations with patients about MRIs and gadolinium exposure.

"This study confirms the recommendation to assess whether or not the benefits outweigh the risks when ordering an MRI with gadolinium in a pregnant patient," Klugman said.

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