Prediction of Postnatal Outcomes in Fetuses With Isolated Congenital Diaphragmatic Hernias Using Different Lung‐to‐Head Ratio Measurements

Objectives The purpose of this study was to compare different methods for measuring the fetal lung area‐to‐head circumference ratio and to investigate their prediction of postpartum survival and the need for neonatal extracorporeal membrane oxygenation (ECMO) therapy in fetuses with isolated congenital diaphragmatic hernias. Methods This prospective study included 118 fetuses of at least 20 weeks' gestation with isolated left‐sided congenital diaphragmatic hernias. The lung‐to‐head ratio was measured with 3 different methods (longest diameter, anteroposterior diameter, and tracing). To eliminate the influence of gestational age, the observed‐to‐expected lung‐to‐head ratio was calculated. Receiver operating characteristic (ROC) curves were calculated for the statistical prediction of survival and need for ECMO therapy by the observed‐to‐expected lung‐to‐head ratio measured with the different methods. Results For survival and ECMO necessity 118 and 102 cases (16 neonates were not eligible for ECMO) were assessed, respectively. For prediction of postpartum survival and ECMO necessity, the areas under the ROC curves and 95% confidence intervals showed very similar results for the 3 methods for prediction of survival (tracing, 0.8445 [0.7553–0.9336]; longest diameter, 0.8248 [0.7360–0.9136]; and anteroposterior diameter, 0.8002 [0.7075–0.8928]) and for ECMO necessity (tracing, 0.7344 [0.6297–0.8391]; longest diameter, 0.7128 [0.6027–0.8228]; and anteroposterior diameter, 0.7212 [0.6142–0.8281]). Comparisons between the areas under the ROC curves showed that the tracing method was superior to the anteroposterior diameter method in predicting postpartum survival (P = .0300). Conclusions Lung‐to‐head ratio and observed‐to‐expected lung‐to‐head ratio measurements were shown to accurately predict postnatal survival and the need for ECMO therapy in fetuses with left‐sided congenital diaphragmatic hernias. Tracing the limits of the lungs seems to be the favorable method for calculating the fetal lung area.