Fetal MRI

Magnetic resonance imaging (MRI) is a technique for imaging or making pictures of internal structures in the body. The science of how the pictures are made is beyond the scope of this article, but no x-rays or so-called ‘ionizing radiation' are used in the process and as such it is felt to be a safe technique. Find more general information on MRI here.

MRI has been used increasingly over the last 20 years to show details of the inner body that could not be seen well with available x-ray or ultrasound (sonogram) equipment. While x-rays are excellent for looking at bones because bones absorb x-rays much more than the surrounding tissues, x-rays are not very good for looking at soft tissues within, or next to, other soft tissues, like a baby within its mother. Also, we know that x-rays themselves can be harmful, so we minimize exposure to them as much as possible.

This fetal MRI shows an early normal pregnancy with a hand in front of the face and a leg extended.

Ultrasound is excellent for looking at internal things that are liquid surrounded by solid (like the outline of a baby within the bag-of-waters or amnion) or things full of liquid (like the heart or kidney), but again not so good for looking at soft tissues within, or next to, other soft tissues like the different parts of the brain, or muscles, nerves and so on. For making clear pictures of the various solid internal parts of the body as well the bones and liquid parts, the MRI can be excellent.

MRI has been used medically for about 20 years in adults and increasingly in pediatrics over the last 10 years. In that time, studies have revealed no harmful effects from MR imaging. With that reassurance, MR imaging is now being used to help answer questions of fetal anatomy or structure before birth when it will aid in making medical decisions or planning critical care. Because of the cost of MR imaging and the relatively short safety experience in pregnancy, it is not used when the information is not time critical (such as when it could be as usefully obtained after delivery) or will not potentially change the management of the pregnancy. The American College of Radiology has issued detailed guidelines for the use of MRI in pregnancy, and Children's Memorial Hospital follows and supports these guidelines.

At Children's Memorial Hospital, the Medical Imaging department has MRI equipment that is ideally suited to doing fetal studies because of the rapid speed at which the images are made. This is important as a fetus inside the mother doesn't hold still for long. The department also has sub-specialists in pediatrics, such as pediatric neuroradiologists, who are expert in interpreting images of babies and the developing fetus.

Decisions as to the usefulness of MR imaging to a given pregnancy are best made by consultation between the mother's maternal fetal medicine specialist and the MRI doctors here. Cynthia Rigsby, MD , is the head of body MRI, and John Curran, MD , is the head of Neuro MRI (head, brain, and spine). Francine Kim, MD , is the Neuro MRI contact for fetal cases.