Fig. 4. Fetus with congenital diaphragmatic hernia (CDH). (a) Measurement of the Lung-to-Head Ratio in a section through the so-called four chamber view with the so-called “longest axis method”: the contralateral lung is measured by multiplying the lung’s longest axis by the longest measurement perpendicular to the former one. Its value is proportionated over the head circumference (b), measured in the standard biparietal view, showing two symmetrical hemispheres, the cavum septum pellucidum at one third of the fronto-occipital diameter and the posterior horns of the lateral ventricles. (c) Herniation of the liver. The major vessels help in its identification. (d) MR images of a fetus with CDH in the second trimester. L = lung; Li = liver, S = stomach, Sb = small bowel.