Morphological markers of pulmonary hypertension in a girl born at 26 weeks of gestation with MRI performed at post-menstrual age 38 weeks (12 weeks old). Axial MRI bright-blood image through the main pulmonary artery and the ascending aorta demonstrates a 9-mm main pulmonary artery and a 6-mm aorta, resulting in a ratio of 1.5:1. A ratio of 1.3:1 or greater, in the absence of a larger left-to-right shunt, is very specific for pulmonary hypertension