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When you have a scan, such as a CT scan or MRI, a dye may be used to help get clearer images of your body – this dye is called contrast. This helps doctors see what is happening inside your body and may be crucial for an accurate diagnosis. However, if you are pregnant or breastfeeding, you may have concerns about the safety of this dye for your baby.Ìý

There are two main types of contrast agents that are used routinely:

• Gadolinium-Based Contrast Agents (GBCAs): These are used primarily in MRI scans. Gadolinium is a metal that helps improve the visibility of internal tissues and blood vessels in the images.
• Iodinated Contrast Agents: These are mainly used in CT scans and contain iodine, which enhances the contrast of blood vessels and organs in the images.

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Benefits:

You might be having diagnostic imaging for a variety of reasons, such as:

• Suspected venous thromboembolism (blood clot in your leg or lungs)
• Suspected cancer
• Acute neurological events
• Vascular emergencies
• Traumatic injuries

Your doctors will explain why this is indicated in your particular case. Contrast helps make images clearer and can be critical for obtaining the right diagnosis, allowing your doctor to make better decisions for both your health and your baby’s health.

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Things to consider?

In pregnancy:

• Gadolinium-Based Contrast Agents (GBCAs): GBCAs are used in MRI and can cross the placenta. While research in humans is limited, studies in animals have not shown significant harm. However, there is a small theoretical risk that the dye could separate in the amniotic fluid and affect the baby’s development, but there are no confirmed cases of harm in humans.

There is also a very rare condition called Nephrogenic Systemic Fibrosis (NSF) that can happen in people with serious kidney problems after receiving GBCAs. While there are no reports of NSF in pregnant women or babies that have been exposed, those with kidney issues should be carefully monitored. GBCA administration in pregnancy should only proceed when deemed clinically critical, and when alternative imaging modalities are either unavailable or inadequate.

• Iodinated Contrast Agents: Used in CT scans, these agents also cross the placenta. While there is no proven increase in birth defects or health problems in babies, there is a theoretical risk that it could affect the baby’s thyroid gland, especially with higher doses. This is not a common issue with modern contrast agents, and no additional fetal surveillance is required.

In breastfeeding:

• Both Gadolinium-based and Iodinated contrast agents pass into breastmilk in very small amounts, with only a tiny fraction being absorbed by the infant (less than 0.0004% for GBCAs and less than 0.01% for iodinated agents). No adverse effects have been reported in babies who were breastfed after the mother had contrast media.

However, if you are concerned, you might opt to pause breastfeeding for 12 to 24 hours, though this is generally not necessary. If you choose to stop breastfeeding, expressing and discarding milk during this time will help maintain your supply and avoid mastitis.

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Alternatives:

If you are concerned about the use of contrast media, there are some alternatives to contrast-enhanced imaging:

• Non-contrast imaging: Ultrasound or CT/MRI without contrast can sometimes be used as an alternative, but they might not always provide an adequate level of detail for certain conditions.
• Waiting: In some cases, it might be possible to delay imaging until after pregnancy or breastfeeding, particularly if the condition is not an emergency. However, waiting could mean a delay in diagnosis, which might be risky if the condition requires urgent attention.

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What happens next?

Make sure you have a conversation with your healthcare provider about the reasons they are recommending imaging and the alternatives.

If you decide to go ahead with the scan and you are pregnant, your baby should not need any extra checks or monitoring only because you have had imaging. If you are breastfeeding, it is safe to continue feeding your baby as normal after the scan. However, if you would prefer not to for 12–24 hours after the contrast is given, you can choose to express and discard your milk during that time. The healthcare team can support you with this to help keep up your milk supply and reduce the risk of discomfort or mastitis.

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Signposts and sources of information:

• The Royal College of Radiologists (2019). Guidance on gadolinium-based contrast agent administration to adult patients.
• The Royal College of Radiologists (2019). Guidance on screening and symptomatic breast imaging. Fourth edition.
• The Royal Australian and New Zealand College of Radiologists (2018). Iodinated Contrast Media Guideline, Version 2.3.
• American College of Radiology (2024). ACR Manual on Contrast Media.
• Ray JG, et al. (2016). Association between MRI exposure during pregnancy and fetal and childhood outcomes. JAMA, 316(9):952-961.
• The Breastfeeding Network. MRI Scans and Breastfeeding.
• The Breastfeeding Network. Computed Tomography (CT) Scans
• National Institutes of Health. Drugs and Lactation Database (LactMed®).

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Note. This document uses the term women throughout, but this term should be taken to also include people who do notÌý identify as women but who are pregnant, in labour and in the postnatal period.

Our Maternity Information Leaflets for parents and service users are reviewed regularly by parents and service users. If you have any comments/feedback about this leaflet or are interested in looking at future leaflets, please contact our Maternity & Neonatal Voices Partnership (MNVP)Ìý

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