Application of Lung Volume Measurement by Three-dimensional Ultrasonography for Clinical Assessment of Fetal Lung Development

Objective. To prepare nomograms for normal fetal lung volume using three‐dimensional ultrasonography and to evaluate the possibility of clinical applications of this procedure. Methods. One hundred twenty‐five healthy neonates with birth weights within ±1.5 SD (group A), 9 neonates with intrauterine growth restriction (birth weight less than –1.5 SD) but no severe respiratory disturbance at birth (group B), and 10 neonates with severe respiratory disturbance but no intrauterine growth restriction (group C) were studied. With the use of a three‐dimensional ultrasonographic device, continuous B‐mode images centering on the fetal thorax were acquired as volume data. Analytical software was used to repeatedly trace the contours of bilateral fetal lungs on transverse slices to calculate the lung volume. Results. In group A, the total volume of normal fetal lungs can be expressed by the second‐degree regression equation: 0.08 × (gestational week – 30.1)2 + 3.28 × gestational week – 67.2 (R = 0.909; P < .001). The lung volumes of groups B and C were below the 25th and 2.5th percentiles, respectively, of this regression curve. For the same case, the lung volume increased with gestational week in group B but remained unchanged or even decreased in group C. The total volume of normal fetal lungs can also be expressed by the linear regression equation: 0.02 × estimated fetal weight + 0.29 (R = 0.902). The lung volumes of groups B and C were distributed below and above, respectively, the 2.5th percentile of the regression line. Conclusions. This analytical method may be applied to evaluate lung development.