Contrast media, radionuclides and diagnostics

4.14.1

X-ray studies, ultrasound, and magnetic resonance imaging

X-ray studies, ultrasound and magnetic resonance imaging (MRI) – independent of the organ being studied – do not require an interruption of breastfeeding. This also applies to mammography and computed tomography without contrast media. Limitations apply for iodine- and gadolinium-containing contrast media and radioisotopes (see below).

4.14.2

Iodine-containing contrast media

Problematic for the infant is the amount of free iodine in the contrast medium, which is normally under 1% of the total amount of contrast medium. This amount is determined by production and can increase during storage. Once administered, more free iodine may be released as a result of de-iodizing enzymes in the mother’s or the infant’s body. The effect of free iodide on the infant’s thyroid depends on the iodine saturation before the application of contrast media. In a latent deficiency status, flooding (e.g. from the contrast medium) with iodine is more likely to lead to an effect on function than in a well-balanced iodine state.

The significance of the iodine transfer to the baby after administration of iodine containing contrast media to the breastfeeding mother cannot be adequately determined by simply measuring iodide, or contrast medium iodine in the infant’s urine. The individual situation can only be precisely described with an assessment of the infant’s iodine uptake and thyroid function.

Gross impairment of the breastfed infant following contrast administration to the mother is unknown. With direct diagnostic use, particularly in infants under 3 months of age, transient hypothyroidism has been described ( ). The effect can be due to discrete actions on the sensitive development of the brain in infancy, and usage should be avoided. However, since breastfed children only receive about 0.01% of a therapeutic infant dose of an iodine-containing contrast medium via the mother’s milk, no serious consequences would be expected. In a review examining the effects on thyroid function after application of iodine-containing contrast media to neonates, the authors conclude that there is a relevant risk of hypothyroidism especially for preterm infants ( ). After oral application of loxitalamic acid 8 days postpartum to the mother, an increase in TSH (just above normal reference values) in the fully breastfed infant was noted. The level returned to normal after 10 days and no clinical abnormalities were noted in the child (unpublished data from Berlin TIS).

The water-soluble iodine-containing contrast media, meglumine amidotrizoate and sodium amidotrizoate , iodamide , iohexol and metrizamide , administered intravenously, appear in the milk available to a fully breastfed baby for a relative dose considerably under 1% ( ).

With iohexol and metrizoate , did not expect an appreciable exposure in the breastfed infant requiring a limitation of breastfeeding. This global estimate seems questionable, since one of the four subjects in their study with ongoing high iodine concentrations of up to 141 mg/L milk, was not considered in the study summary. The authors calculated half-lives in the milk of 15–108 hours for iohexol and metrizoate. The serum half-lives of water-soluble contrast media of about 2 hours are considerably shorter. Metrizoate is no longer approved for intravenous administration.

For the fat-soluble iopanoic acid , used for biliary duct imaging, 7% of the maternal weight-related dose was calculated for the breastfed infant in an older study ( ). Iopanoic acid is also no longer regularly used.

There are no data available on other iodine-containing contrast media such as iobitridol , iodixanol , iomeprol , iopamidol , iopentol , iopodate , iopromide , iothalaminic acid , iotrolan , iotroxic acid , ioversol , ioxaglinic acid , loxitalamic acid , lysine amido-trizoate .

The European Society of Urogenital Radiology ( ) recommends that breastfeeding may be continued after application of iodine-based contrast agents to the mother. The American College of Radiology ( ) is of the same opinion; although it cautions that an informed decision to temporarily stop breastfeeding for 24 hours should be left to the mother. The guideline especially states that there is no established value to stop breastfeeding beyond 24 hours.