Evaluation of normal fetal branch pulmonary artery diameters measured by ultrasonography: a comparison with congenital diaphragmatic hernia.

OBJECTIVE The aim of this study was to examine the size of fetal branch pulmonary artery (PA) diameters in normal growth fetuses. METHOD Fetal PA diameters were measured in 175 normal fetuses between 18 and 40 weeks of gestation from 2005 to 2006. In addition, 4 fetuses with left-sided congenital diaphragmatic hernia (CDH) from 2001 to 2006 were retrospectively reviewed. Branch PA diameters were measured from a cross-sectional image at the level of the three-vessel view (main PA, ascending aorta and superior vena cava) to demonstrate the long axis of both branch PAs whenever possible. RESULTS Both the left and right PA diameters were found to correlate strongly with the advancing gestational age (r = 0.78, p < 0.01, respectively). Left pulmonary artery to main pulmonary artery (LPA/MPA) ratio and right pulmonary artery to main pulmonary artery (RPA/MPA) ratio were calculated. These two parameters were almost constant throughout gestation. LPA in fetal left CDH was smaller than control. Both LPA/MPA and RPA/MPA were within the normal range in most cases. CONCLUSIONS It is important to establish the normal range of branch PA diameters and it appears to be useful to compare the branch PA diameters in normal fetuses with that in cases of pulmonary hypoplasia.