Prediction of survival in fetuses with left-sided congenital diaphragmatic hernia: Which method is better using MRI observed to expected total fetal lung volumes?

Objective: The Observed to Expected Total Fetal Lung Volume (O/E-TFLV) ratio, calculated using fetal MRI, is a common method to assess pulmonary hypoplasia severity in congenital diaphragmatic hernia (CDH). However, its accuracy may be affected by uncertain gestational age (GA), inaccurate pregnancy dating, or abnormal fetal growth. This study aimed to evaluate whether GA determined by first-trimester dating or fetal size at imaging affects the ability of O/E-TFLV to predict 6-month survival in fetuses with isolated left-sided CDH. Methods: Retrospective cohort study of fetuses with isolated left-sided CDH. O/E-TFLV was calculated using GA based on CRL (O/E-TFLVGA) or fetal size-determined GA (O/E-TFLVEFW) at the time of MRI. Prediction of survival was evaluated using ROC curves and logistic regression analyses adjusting by CDH severity and liver herniation. Results: Ninety-seven fetuses underwent third-trimester MRI, with seventy-nine (81 %) also having second- trimester MRI. At six months, 80/97 (82.5 %) were alive. No significant differences were observed between O/E-TFLVGA and O/E-TFLVEFW during the second (31.5[2-74]%vs. 31.7[2.5-86]%, p = 0.71) or third trimester (33.6[0.1-134.3]% vs. 31.7[8-105]%, p = 0.55). Higher O/E-TFLVGA and higher O/E-TFLVEFW were associated with higher chances of survival (Second trimester: O/E-TFLVGA: Odds Ratio 1.09 [95 %CI: 1.02-1.20], p = 0.04; O/E-TFLVEFW: 1.10[1.01-1.20], p = 0.04; Third trimester: O/E-TFLVGA: 1.06[1.02-1.16], p = 0.04; O/ETFLVEFW: 1.03[1.01-1.09], p = 0.04). No significant differences were found in predictive accuracy between O/ETFLVGA and O/E-TFLVEFW based on Area Under the Curve (AUC) analysis (Second trimester: p = 0.65; Third trimester: p = 0.72). Conclusion: There were no difference in the prediction of survival in isolated left-sided CDH fetuses using O/ETFLV regardless of the method used to calculate O/E-TFLV.