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How MRIs Work



The MRI scanner causes the nuclei of the hydrogen atoms in your body to align by creating a powerful, uniform magnetic field. The atoms then absorb energy from precisely tuned radio pulses and emit radio signals. The scanner receives those signals and converts them into images which can be analyzed by a doctor.

Are MRIs Safe During Pregnancy

MRI scans do not use radiation, and they are a low-risk procedure. Thousands of pregnant women have MRI scans performed, without any harm coming to the mother or baby. The most difficult part of an MRI for most expectant mothers is that they require you to remain still in the tube for up to 40 minutes, depending on the part of the body being scanned.

In some MRIs, it is necessary to use a contrast material to make the scan easier to read. This contrast material is called gadolinium, and it is injected into your veins in order to highlight certain parts of the scan. While the use of this contrast material is routine in patients that are not pregnant, it will only be used during pregnancy if it is absolutely necessary.

The MRI scanner can be quite noisy, but according to a study conducted in 2010 by Reeves et al. the noise produced by the scanner is not enough to damage the hearing of a baby even during the second or third trimester. In addition, the electromagnetic fields produced by the scanner have not been found to be harmful. The MRI is thought by many to be one of the safest and least intrusive scans in modern medicine.

Why Might a Doctor Order an MRI?

Your doctor may choose to order an MRI if you are experiencing symptoms that require medical treatment, or you have had an examination performed and the results are not clear enough on their own. If your doctor orders an MRI during pregnancy, this means that they feel the symptoms you are reporting are serious enough that they require treatment before the birth of your baby.

If your doctor wants to examine your baby, they will choose an ultrasound first. If the ultrasound image is not clear enough, or if they want to examine parts of your body, rather than the baby, then they may recommend an MRI instead.

If you have any concerns about the safety of the MRI scanner, or any other treatments, talk to your doctor. They will be happy to explain why they have ordered the procedure, and to lay out the risks and benefits of that procedure.