Volumetric growth of the lungs in human fetuses: an anatomical, hydrostatic and statistical study

The prenatal assessment of lung volume is becoming increasingly important in determining survival in both preterm infants and newborns affected by pulmonary hypoplasia. This study aimed to examine the lung volumes in the human fetus at varying gestational ages.

Using anatomical, hydrostatic (water displacement according to Archimedes' patent) and statistical methods (one-way ANOVA test for paired data and post-hoc Bonferroni test, Kolmogorov-Smirnov test, Levene's test, Student's t test, regression analysis), volumes of the right and left lungs were measured in 67 human fetuses of both sexes (35 males, 32 females) aged 16-25 weeks, derived from spontaneous abortions and stillbirths.

No male-female differences concerning the right and left pulmonary volumes were found. The mean volume of the right lung increased from 1.43 ± 0.25 to 8.45 ± 2.66 cm(3), according to the cubic function y = -1.592 + 0.0007 × age(3) ± 0.851 (R (2) = 0.84). The volumetric growth of the left lung, from 1.24 ± 0.22 to 6.78 ± 3.03 cm(3), followed the cubic model y = -1.110 + 0.0005 × age(3) ± 0.794 (R (2) = 0.78). The total pulmonary volume increased from 2.67 ± 0.47 to 15.22 ± 5.58 cm(3), in accordance with the cubic model y = -2.729 + 0.0012 × age(3) ± 1.598 (R (2) = 0.83). The mean volumes of the right and left lungs accounted for 54.9 ± 2.0 and 45.1 ± 2.0 %, respectively, of the total lung volume.

No sex differences are found between the lung volumes in the fetus. The growth of fetal lung volume follows a three-degree polynomial function. Throughout the analyzed period the two lungs grow proportionately to each other, with the volumetric predominance of the right lung. The lung volumes in the fetus are of great relevance in the evaluation of the normal pulmonary growth and the diagnosis of pulmonary hypoplasia.