Lung to Head Ratio

Our first meeting with Dr. Ball was very similar to our appointment with Dr. Herbst. He performed another ultrasound (this would be the routine for the summer). He confirmed the severity of the hernia and took some measurements of our baby's head and lungs, introducing us to a measurement called Lung to Head Ratio (LHR).

Lung to Head Ratio

To measure the lung-to-head ratio one measures the length and width of the right lung and multiplies it. This gives the right lung area. Then, you divide the value of right lung area by the value of the head perimeter.

For example (as seen in the diagram):

• Right lung measures: 21 mm x 10 mm = 210 mm2 (forget the units of measurement at this point)

• Head perimeter measures: 200 mm

• Lung to head ratio: 210/200 = 1.05

Our Son's LHR

Our son's LHR was 0.6, considerably less than 1.0. So what does that mean?