Objective: The objective of our study was to evaluate the potential of the sonographic fetal lung volume-body weight ratio to predict neonatal deaths and pulmonary hypoplasia in fetuses with isolated congenital diaphragmatic hernia (CDH).
Subjects and methods: Between January 2002 and December 2004, 40 fetuses with isolated CDH and 450 control subjects were prospectively evaluated in two centers. Fetal lung volumes were estimated on 3D sonography using the rotational technique and fetal weight on 2D sonography using the Hadlock equation. The ratio of sonographic fetal lung volume to body weight was calculated in each case and was correlated with neonatal deaths using the Mann-Whitney U test. Accuracies of the ratio in predicting neonatal deaths and pathologic diagnosis of pulmonary hypoplasia were also evaluated.
Results: The ratio of sonographic fetal lung volume to body weight is constant throughout gestation, with a mean value of 0.025. The ratio was significantly lower in neonates that died (median, 0.009; range, 0.004-0.021) than in those that survived (median, 0.011; range, 0.008-0.020) (p = 0.018). Pulmonary hypoplasia was suspected prenatally in 34 of 40 (85.0%) fetuses with CDH, in all cases of death (100%), and in seven of nine (77.8%) neonates that survived. At autopsy, pulmonary hypoplasia was diagnosed in 19 cases (86.4%). Accuracies of the ratio in predicting neonatal deaths and pulmonary hypoplasia were 64.5% (20/31) and 86.4% (19/22), respectively.
Conclusion: The sonographic fetal lung volume-body weight ratio can be used more accurately to diagnose pulmonary hypoplasia than to predict neonatal deaths in fetuses with isolated CDH. Further studies are necessary to show the prevalence of pulmonary hypoplasia in fetuses with isolated CDH and its importance for predicting neonatal deaths.