Fetal MRI Adds Clarity to the Ultrasound Image
"MRI is especially useful in confirming diagnosis," says Frates. "It is harder to see inside the brain as the fetus gets older if you are using just ultrasound, but MRI overcomes this difficulty."
Frates adds that when ultrasound indicates a problem, "it is not unusual to have an MRI scheduled for immediately after birth. But many of these fetuses are quite ill when they are born and are on ventilators. It is difficult to take an ICU [intensive care unit] baby and put him or her inside the MRI. But when the fetus is inside the mother, it is in a stable environment, and we can put the mother inside the magnet. It's a better option."
Coakley and Frates both say there is no danger to pregnant women from MRI but MRI is not useful before 18 weeks of pregnancy because the fetus moves too much before that time. They add that mothers do not need to take medication to still the fetus, but, Frates says, "we tell the mother not to eat for several hours, because as anyone who has been pregnant knows, sugar really excites the fetus."
Coakley says that MRI imaging at his institution costs about $1,500, and he says insurers have not objected to paying for it. "In the case of the baby with liver disease, the MRI study was a lot cheaper than a transplant," he says.
Frates says that her institution is in the very early stages of a study to determine the utility of fetal MRI to measure lung maturity. Currently, lung maturity is measured by amniocentesis, the removal of some of the fluid surrounding the fetus, "but that is an invasive procedure, and if the mother doesn't have enough amniotic fluid, it can't be done."
- When a fetal ultrasound is inconclusive, an MRI can be a useful addition for making a diagnosis.
- It is easier to perform an MRI on a pregnant woman than on a newborn, who would probably be in intensive care, and there are no negative effects on the mother or child.
- The imaging technique is able to confirm diagnosis and sometimes provide additional information in babies with CNS disorders, genital/urinary abnormalities, and possibly lung maturity problems.