Background: There are many causes affecting diaphragmatic height including normal variation and pathology. Both elevation and depression of the diaphragm imply various pathologies. In our knowledge, no previous study of newborn evaluated the different height of diaphragms. Using adult’s reference value in interpretation of newborns’ chest remains doubtful because of different imaging technique.
Objective: To assess diaphragmatic height and measure different height of diaphragms in the chest radiographs of newborns.
Material and Method: A retrospective review of chest radiographs was performed on 100 newborns (age less than 1 month) who were diagnosed of transient tachypnea of the newborn (TTNB) that had respiratory distress and abnormalities in chest radiographs disappeared. The diaphragmatic positions and different diaphragmatic height were evaluated in relation to thoracic vertebra and posterior rib.
Results: Right diaphragmatic dome was positioned at 8.17+0.72 thoracic vertebral levels below the top of first thoracic vertebra and 8.28+0.78 crossing rib levels. Left diaphragmatic dome was positioned at 8.87+0.71 thoracic vertebral levels and 8.91+0.29 crossing rib levels. The different height of diaphragms was 0.70+0.34 thoracic vertebral body and 0.63+0.29 intercostal spaces. No newborn had the left diaphragmatic dome higher than the right side.
Conclusion: The different diaphragmatic height in newborns is less than 1 intercostal space or 1 thoracic vertebral level.
This knowledge is useful for assessment of chest radiographs.

Keywords: Newborn, Diaphragm, Chest radiograph