Patient Information: Fetal MRI
What to expect
The morning of the exam:
The preparation for a fetal MRI may include limiting caffeine intake and concentrated carbohydrates for several hours prior to the exam. Some institutions require a patient to have nothing by mouth for four hours prior to the exam. Both caffeine and large amounts of sugar can stimulate the fetus, thus making images blurry.
When you arrive at the facility:
The exact time to arrive will be determined by the facility at which you are having your exam. You should allow time to fill out any necessary paperwork. You will be asked about any metal/foreign objects in your body such as prosthetic joints or heart valves, pace makers, or nerve stimulators. It would be helpful to have as much information about these devices as possible.
During the fetal MRI:
Imaging for a fetal MRI usually takes less than an hour, but the length of time may vary based on the reason for imaging, the activity level of the fetus, and the comfort level of the mother.
The mother will be asked to lie on her back or on her left side during the exam. Some women are concerned that they may feel claustrophobia while being inside the MRI machine. You should be aware that the magnetic waves are very small and the machine needs to be close in order to sense them, but that there is nothing in the machine that moves except the table on which you are lying. The space cannot close or get smaller. You will always have a way to communicate with the technologist should you become uncomfortable. You will be able to stop the exam at any time.
The MRI machine can be very loud. Expect to hear loud noises and banging. You will be asked to wear earplugs. Some facilities will allow you to listen to music or watch movies during the exam.
In general, there will be no need for medication so an IV will not be started. No intravenous contrast will be necessary for the exam.
After the fetal MRI:
You can resume your normal activities and diet. No restricitions should be placed on you due to the MRI itself.
Risks of fetal MRI:
Fetal MRI has been performed for over 20 years and there are no known risks to the fetus. Fetal MRI uses magnetic and radiowaves to capture images of the baby and does not use ionizing radiation like computerized tomography (CAT scan) and x-rays do. Additionally, no intravenous contrast material (dye), special medication or sedation is needed to perform the exam. The MRI will not cause you or your fetus pain.
Because the fetus is extremely small and therefore difficult to image with MRI in the first trimester, and because we like to take extra precautions to avoid the noise that comes with MR imaging regarding the developing ear, fetal MRI is performed only in the second and third trimesters.
Benefits of fetal MRI:
Although ultrasound (US) is the primary means of imaging a fetus, it can be limited in some of the information it provides. MRI can sometimes give more information when an abnormality is detected on US. For instance, MRI shows excellent detail of the developing brain compared to US. In many cases, fetal MRI can provide more information about the severity of an abnormality and can lead to more informed decision making by doctors and patients with regard to prognosis.
What the information gathered during the MRI will be used for:
As alluded to above, with the additional information that an MRI can provide, you and your doctor will have a better idea of what to expect during the remainder of your pregnancy, after birth and what special treatment, if any, your baby may need. The information may allow for more informed decisions about birth planning (Caesarean section vs. vaginal delivery) and whether delivery in a specialized center is recommended. In a few, very select circumstances, therapy may be available to treat an abnormality while the fetus is still in the uterus.
The following are links to fetal care centers around the nation, at which there may be more information available to you regarding specific fetal diagnoses made by MRI.