Benefits and risks of MRI in pregnancy.

Ultrasound remains the modality of choice in imaging the fetus due to its availability, safety, and low cost. With advances in technology, however, magnetic resonance imaging (MRI) has become an important adjuvant in the evaluation of the fetus. MRI is not limited by fetal lie, oligohydramnios, overlying bone, or obesity. MRI can image the fetus in any plane, providing a large field of view of the fetus and placenta with excellent soft tissue resolution of the brain, airway, lungs, and abdomen. Advanced techniques are being developed that provide volumetric data, spectroscopy, and functional images. MRI has its own set of challenges with a lack of consensus regarding its utility and safety. Artifact from the moving fetus and breathing mother limits the sequences available. While there is currently no evidence that fetal MRI produces harmful effects, long-term safety regarding radiofrequency fields and the loud acoustic environment continues to be studied. In this review, the benefits and potential risks of fetal MRI will be discussed.