Prenatal diagnosis of fetal anomalies using ultrasound and MRI.

In conclusion, it is unlikely that MRI will replace ultrasound as the primary obstetric imaging modality in the near future. Ultrasound has a proven record of accuracy and safety in addition to its easy access and low cost. MRI has promise, however, in providing crucial information in patients with underlying medical or surgical conditions that would ordinarily require ionizing radiation for evaluation. Currently, MRI is helpful in evaluating gross fetal anomalies and disturbances of fetal growth and development when ultrasound is limited by oligohydramnios or maternal obesity. Further experience is required to determine the value of spectroscopy and quantitative relaxation times regarding fetal metabolism and fetal well-being. Technologic improvements and software updates will reduce imaging time and increase spatial resolution, thus rendering MRI more competitive with existing imaging techniques. The ultimate role, however, that MRI will have in the evaluation of the fetus is currently undefined.