Medical Imaging During Pregnancy: What's Safe?

The single most important rule: if you are pregnant, might be pregnant, or are trying to conceive, tell your referring doctor and the imaging clinic before any scan.

Clinics routinely ask women of childbearing age about pregnancy before X-rays, CT scans, and nuclear medicine tests. This isn't a formality - it allows the team to choose the safest test, adjust the technique, or postpone imaging that isn't urgent.

If you find out you're pregnant after booking a scan, call the clinic. In many cases the scan can still go ahead safely, be swapped for a different test, or simply be rescheduled. Your doctor and the radiologist will weigh the benefit of the scan against any risk to the pregnancy.

Ultrasound is the standard imaging test during pregnancy. It uses sound waves rather than radiation, and decades of use have shown no harmful effects on mother or baby when performed for medical reasons.

Beyond routine pregnancy scans (dating scans, the 12-week and 20-week scans), ultrasound is also the first choice for investigating other problems during pregnancy - abdominal pain, gallstones, blood clots in the legs, and thyroid or breast lumps.

Because it's safe to repeat, ultrasound can be used as often as clinically needed throughout pregnancy. Many pregnancy ultrasounds are bulk-billed with a valid referral, and you can use Radly to compare clinics near you and check bulk billing before you book.

MRI does not use ionising radiation, and it is generally considered safe during pregnancy when the scan is medically needed. It's often used when ultrasound can't answer the question - for example, to assess appendicitis, pelvic conditions, or the baby's brain and spine in specialist settings.

A few points to know:

• Some doctors prefer to avoid non-urgent MRI in the first trimester as a precaution, though there's no proven harm. • Gadolinium contrast dye is usually avoided in pregnancy unless the benefit clearly outweighs the risk. Most pregnancy MRIs are done without contrast. • The scan itself is loud and you'll lie still for 20-60 minutes, so let staff know if you're uncomfortable lying flat late in pregnancy.

Your doctor and the radiologist will decide together whether MRI is the right test.

X-rays and CT scans use ionising radiation, so they're approached more carefully in pregnancy - particularly scans of the abdomen and pelvis, where the baby would be in the imaging field.

Some context helps here. Scans of areas away from the uterus - a chest X-ray, a dental X-ray, or a CT of the head - deliver a very small dose to the baby, and can usually be done safely with shielding and careful technique. A single diagnostic scan almost never delivers enough radiation to harm a developing baby.

That said, doctors avoid abdominal and pelvic CT during pregnancy unless it's genuinely necessary - for example, in serious trauma or when a life-threatening condition is suspected and no alternative test will do. In those situations, the benefit of an accurate, fast diagnosis outweighs the small radiation risk.

If you're breastfeeding, most imaging is completely fine - ultrasound, X-ray, MRI, and CT don't affect breast milk.

Contrast dyes are also less of a concern than many mothers expect:

• Iodinated contrast (used in CT): only a tiny amount passes into breast milk, and current Australian guidance is that breastfeeding can continue as normal. • Gadolinium contrast (used in MRI): similarly, the amount reaching breast milk is minimal, and interrupting breastfeeding is generally considered unnecessary.

Some mothers still prefer to express and discard milk for 24 hours after contrast for peace of mind - that's a personal choice, and clinic staff can talk it through with you. If you're breastfeeding and having a mammogram or breast ultrasound, mention it when booking, as it changes how the images are interpreted.

If you're pregnant or breastfeeding and imaging has been recommended, useful questions for your GP or the clinic include:

• Is this scan urgent, or can it safely wait until after the pregnancy? • Is there an alternative test that doesn't use radiation, like ultrasound or MRI? • Will contrast dye be used, and is it needed? • What precautions will be taken during the scan?

Remember, this guide is general information only - your GP, obstetrician, and the radiologist are the right people to weigh up your individual situation. When you're ready to book, you can use Radly to compare imaging clinics across Victoria, check bulk billing and prices, and find appointment times that suit you.