The Virtual Hydrostatic Test

The hydrostatic test is used to help determine if there has been a live birth. Computed tomography (CT), with its ability to detect and localize air/gas in the body, offers a rapid, noninvasive tool for assessment. Four baby deaths (20 to 25 weeks' gestation) in which the hydrostatic test, radiographs, and CT were performed before autopsy are presented. In 2 cases, considered stillbirths, the lungs and liver sank, and there was no air seen in the lungs or gas in the liver on CT. Histology of the lungs showed collapsed alveoli. In 1 case, concluded to be a live birth, the lungs floated, the liver sank, and air was seen in the trachea, bronchi, and both lungs on CT. Histology of the lungs showed multiple areas of expanded alveoli. In 1 case, where both the lungs and liver floated, the CT showed gas widely distributed in the soft tissues. This reflected decomposition, and no conclusion could be made regarding birth status. Assessment of live birth is a critical and difficult decision. Postmortem CT offers another technique to consider in this determination, and it has significant advantages over radiography. Continued study and correlation with existing methods seem warranted.