Ultrasonographic measurement of fetal lung.

Fetal lung measurements were obtained by ultrasonographic examination on 103 normal pregnancies between 18 and 41 weeks' gestation. A linear relationship between right, left and total lung circumference and gestational age was observed. The chest and heart circumference correlated well with gestational age (p less than 0.001). The ratio of left lung circumference to right lung circumference remained virtually constant throughout gestation. However, the ratios of total lung circumference to chest circumference and heart circumference to chest circumference increased significantly (p less than 0.001) with gestational age.