This is an excellent article that reviews the current knowledge about the use of various iodinated and gadoliniium-containing radio contrast agents used in CT and MRI scans. While the iodinated compounds are probably safe to use in breastfeeding mothers,  there is some concern over the "repeated" use of the metal-containing gadoliniium products used for MRI scans.  Excellent review of this subject.  TWH

SUMMARY from this article:

Different types of contrast agents are used according to the imaging modality. When they are administered to patients who are pregnant or lactating, special considerations need to be taken into account. Iodinated contrast media are considered safe for mothers and newborns. To date, no data suggesting any potential harm to the fetus have been reported. There is no need to stop breastfeeding after the administration of such contrast agents. Barium sulfate has not demonstrated to be teratogenic or result in side effects in patients inadvertently exposed to it during pregnancy. Its use is limited in patients who are pregnant due to the potential teratogenic effects of radiation exposure that entail performing these examinations. Due to its unknown effects on the fetus, contrast-enhanced MR imaging should be limited in patients who are pregnant to instances in which it is absolutely necessary. The administration of GBCAs should be assessed on a case-by-case basis after taking into consideration maternal and fetal risks. Breastfeeding is considered safe after administration of GBCAs due to its low excretion into breast milk, and temporary cessation of breastfeeding is not recommended. Although popular Europeand Asia, one ultrasound contrast agent was just recently approved by the FDA for use in noncardiac studies. Its administration to women who are pregnant is not approved

Magn Reson Imaging Clin N Am. 2017 Nov;25(4):787-797. doi: 10.1016/j.mric.2017.06.010. Epub 2017 Sep 8.

Safety of Contrast Material Use During Pregnancy and Lactation.

Puac P¹, Rodríguez A², Vallejo C², Zamora CA³, Castillo M⁴.

Author information

Abstract

The use of contrast media to image patients who are pregnant has increased during the past decades worldwide. Their use in pregnancy and in patients who are lactating remains a challenging issue for radiologists and other physicians. This article addresses the different types of contrast media that may be used in such patients according to the imaging modality (iodinated contrast media, barium, gadolinium-based, and ultrasound contrast agents), focusing on their adverse effects, potential teratogenic effects, strategies to minimize risks, and current clinical recommendation.

KEYWORDS:

Barium sulfate; Contrast media; Contrast-enhanced ultrasound; Gadolinium-based contrast media; Iodinate-based contrast media; Lactation; Pregnancy

PMID:  28964468