MRI Contrast Agents and Pregnant Patients*

Studies of low molecular weight water-soluble extracellular substances such as gadolinium-based magnetic resonance imaging (MRI) contrast agents in pregnancy have been limited, and effects on the human embryo or fetus are unknown. A standard gadolinium-based MRI contrast agent has been shown to cross the placenta in primates and appear within the fetal bladder within 11 minutes after intravenous administration. It must be assumed that all gadolinium-based contrast media behave in a similar fashion and cross the blood-placental barrier into the fetus.

After entering the fetal blood stream, these agents will be excreted via the urine into the amniotic fluid and be subsequently swallowed by the fetus. It is then possible that a small amount will be absorbed from the gut of the fetus and the rest eliminated back into the amniotic fluid, the entire cycle being repeated innumerable times.

In the study in primates, placental enhancement could be detected up to 2 hours following the intravenous administration of gadopentetate dimeglumine. When gadopentetate dimeglumine was injected directly into the amniotic cavity, it was still conspicuous at 1 hour after administration. There are no data available to assess the rate of clearance of contrast agents from the amniotic fluid.

The American College of Radiology (ACR) Committee on Drugs and Contrast Media has reviewed this issue extensively and has prepared the following summary of information and recommendations.

Gadolinium-Based MRI Contrast Agents and Pregnant Patients
It is known that gadolinium-based MR contrast media cross the human placenta and into the fetus when given in clinical dose ranges. No adequate and well-controlled teratogenic studies of the effects of these agents in pregnant women have been performed. The ACR recommends that all imaging facilities should have policies and procedures to reasonably attempt to identify pregnant patients prior to the performance of the MR exam, and before the use of MRI contrast media in these patients. The ACR has issued a White Paper on MR safety in pregnancy and related issues that is also consistent with the ACR Committee on Drugs and Contrast Media's recommendation for MRI contrast media.

While there is no compelling evidence of teratogenicity or other adverse effect on the fetus of MR imaging or of gadolinium-based MRI contrast agents, neither the safety of the MR environment nor the safety of the MRI contrast agents in pregnant patients has been established. It is therefore prudent for pregnant patients at any stage of pregnancy to be informed of the risk-benefit ratio that may warrant the performance of an MR scan with or without contrast media. The radiologist should confer with the referring physician and document the following in the radiology report or the patient's medical record:

(1) The information requested from the MR study cannot be acquired using other nonionizing radiation imaging modalities (e.g., ultrasonography).
(2) That the information needed affects the care of the patient and fetus during the pregnancy.
(3) That the referring physician is of the opinion that it is not prudent to wait to obtain this information until after the patient is no longer pregnant.

It is recommended that the pregnant patient undergoing an MR examination with contrast material provide informed consent to document that she understands the risk/benefits of the MR procedure to be performed, and the alternative diagnostic options available to her (if any), and that she wishes to proceed.

[*Excerpted with permission from the Runge VM. Chapter 12, Safety of Magnetic Resonance Contrast Agents. In: Magnetic Resonance Procedures: Health Effects and Safety. CRC Press, Boca Raton, FL, 2001, pp. 241-260 and Excerpted with permission from the American College of Radiology, Manual on Contrast Media, 5th Edition, 2004; Reprinted with permission of the American College of Radiology. No other representation of this article is authorized without express, written permission from the American College of Radiology.

Also, please see the new version of this document Manual on Contrast Media, Version 6, 2008 - full version available at www.acr.org]

REFERENCES
American College of Radiology, Manual on Contrast Media, 5th Edition, 2004.

American College of Radiology white paper on MR safety. American Journal of Roentgenology 2002;178:1335-1347.

American College of Radiology white paper on MR safety. 2004 Update and revisions. American Journal of Roentgenology 2004;182:111-1114.

Panigel M, Wolf G, Zeleznick A. Magnetic resonance imaging of the placenta in rhesus monkeys, Macaca mulatta. J Med Primatol 1988;17:3-18.

Runge VM. Chapter 12, Safety of Magnetic Resonance Contrast Agents. In: Magnetic Resonance Procedures: Health Effects and Safety. CRC Press, Boca Raton, FL, 2001, pp. 241-260.

Shellock FG, Kanal E. Safety of magnetic resonance imaging contrast agents. Journal of Magnetic Resonance Imaging 1999;10:477-484.