Fetal MR is indicated when:
1. An abnormality on ultrasound is not clearly defined and more information is sought in order to make a decision about therapy, delivery, or to advise a family about prognosis. Example indications include a potential anomaly in the setting of maternal obesity, oligohydramnios, or advanced gestational age.
2. An abnormality is identifed on ultrasonography and the treating physician desires MR-specific information in order to make decisions about care. An example might include the calculation of MR-derived fetal lung volumes in cases of congenital diaphragmatic hernia.
3. A fetus is significantly at risk for abnormality that will affect prognosis even if no finding is discovered with ultrasound, eg neurologic ischemia after laser ablation of placental anastomoses in Twin-Twin Transfusion Syndrome.