The benefit verses the effect of fetal Magnetic Resonance Imaging has been a controversial subject for years. Magnetic Resonance Imaging is a helpful tool for diagnosis of many diseases and abnormalities, but is it actually harmful to the fetus? Do the benefits of the Magnetic Resonance Imaging outweigh the risks? Ultrasound is the mostly commonly used imaging used in pregnancy, but in certain cases using fetal Magnetic Resonance Imaging in conjunction with ultrasound is very beneficial in planning and strategizing care for the fetus.
Magnetic Resonance Imaging has been proven to help to better characterize mass, show location and extension of the lesion, and to show more detail in certain conditions. Using MRI can help to characterize a mass that is seen on the ultrasound. The MRI helps to give a more detailed image. This is helpful for the doctors to get a better idea of what type of treatment plan they should formulate if it is a mass rather than a shadowing of a bone. Many times the pelvis bone can overshadow and appear as an abnormal mass rather than a bone.
On the subsequent fetal MRI examination, the mass is not only better characterized, but is clearly identified as entirely extra-pelvic. MRI helps in eliminating uncertainty from the ultrasound caused by acoustic shadowing due to fetal pelvic bones. Mass content is also of prognostic importance and is better delineated on MR. 1 MRI is also helpful in determining lesions of the lungs and how large or severe they may be before the baby is born. Not only can the MRI determine the size of the lesions, but it can also determine the lung volume of the fetus.
In fetal life, US is the most important, and usually the only modality required for lesion characterization and for identification of unfavorable prognostic factors. Supplementary MRI is useful in selected complicated cases as it allows accurate determination of the location and extension of the lesion and a better assessment of both the normal and abnormal fetal lung, including lung volume. 2 The renal arteries are better seen in MRI rather than ultrasound in some cases such as oligohydramnios which is when there isn’t enough amniotic fluid present.
The MRI helps to provide a better contrast, producing a clearer image. Although ultrasound is the primary imaging tool in prenatal diagnosis of fetal renal anomalies, the efficacy of ultrasound is decreased in the presence of oligohydramnios, which is a common association with fetal renal anomalies. 3 After my research, I have come to the conclusion that fetal MRI is very beneficial in most cases of abnormalities if the ultrasound doesn’t show enough detail.
It is not necessary in every pregnancy but, MRI should continue to be used in coniunction with ultrasound when necessary for diagnosis or progression of fetus development that cannot otherwise be seen. They have not proven that it causes any harmful effects to the fetus, but it has helped find many abnormalities of the spinal cord, brain, renal arteries, lungs, and many more body organs. Finding these abnormalities before the baby is born is beneficial to help know how serious the situation may be and to be making medical plans of what to do after birth.
MRI provides a clearer image most successfully after the first trimester of pregnancy using low techniques. There is no scientific evidence of risk to the human fetus from MR imaging during pregnancy. MR imaging at 1. 5 T or lower magnetic field strength has been used to evaluate diseases in pregnancy for over 20 years without any documented harmful effects. Magnetic resonance imaging (MRI) has been shown to be useful in the diagnosis of gynecological and obstetric problems during pregnancy and in the setting of acute abdomen during pregnancy.
MRI overcomes some of the limitations of ultrasound, mainly the size of the gravid uterus. 4 MRI has even been proven to help in diagnosis of brain and spinal cord development of the fetus. MRI can delineate the development of the subcortical brain structures at the midtrimester of pregnancy and can obtain the normal measurements of these structures. It can provide certain help in evaluating fetal brain development in the uterus. 5 As mentioned previously, MRI can help attain a clearer image than ultrasound in cases of oligohydramnios and also in obese mothers.
Although it is the primary method of fetal imaging, it cannot provide sufficient information about the fetus in some conditions such as maternal obesity, oligohydramnios and engagement of the fetal head. At this stage, magnetic resonance imaging (MRI) facilitates examination by providing more specific information. 6 MRI is also considered safe for the fetus because it does not require any type of maternal sedation. Fetal MRI was introduced in 1983, but the ultra-fast MRI sequences allow excellent detection of fetal anatomy without the need for maternal sedation.
Recent MRI techniques, considered safe for fetuses, can be obtained during breath holding by the mother instead of maternal sedation. 7 MRI can be used any time during pregnancy, but will show most detailed image after the first trimester. MRI is not used routinely in pregnancy. It is used in situations where nonionizing imaging methods are inadequate or ionizing radiation is required in pregnant women. It is not recommended during the first trimester. 8
Overall Magnetic Resonance Imaging can be very helpful when combined with Ultrasound. Meanwhile MRI produces no harmful effects to the fetus that have been proven. MRI helps to better characterize a mass in the fetus body, determine the location and size of a lesion, and to show more detail in certain special cases. I think that MRI has been helpful a helpful tool for diagnosis to many expecting mothers in the past, and will continue to help diagnosis and determine a plan of action for many pregnancies in the future.