Does prediction of neonatal mortality by the observed/expected lung-to-head ratio changeduring pregnancy in fetuses with left congenital diaphragmatic hernia?

Aim: to evaluate prediction of neonatal mortality in fetuses with isolated left congenital diaphragmatic hernia (CDH) when the observed/expected lung-to-head ratio (O/E LHR) was estimated at two different gestational time points during pregnancy. Methods: Forty-four (44) fetuses with isolated left CDH were included. O/E LHR was estimated at the time of referral (first scan) and before delivery (last scan). The main outcome was neonatal death due to respiratory complications. Results: There were 10/44 (22.7%) perinatal deaths. The areas under (AU) the ROC curves were: first scan, 0.76, best O/E LHR cut-off 35.5% with 76% sensitivity and 70% specificity; last scan, AU ROC 0.79, best O/E LHR cut-off 35.2%, with 79.0% sensitivity and 80% specificity. Considering an O/E LHR cut-off <= 35% to define high risk fetuses at any examination, prediction for perinatal mortality showed: 79% sensitivity, 73.3% specificity, 47.1% positive and 92.6% negative predictive values, and 3.02 (95% CI 1.59-5.73) positive and 0.27 (95% CI 0.08-0.96) negative likelihood ratios. Prediction was similar in the two evaluations as 13/15 (82.1%) of fetuses considered at risk had an O/E LHR <= 35% in the two examinations; in the remaining 4 cases, two were identified only in the first and two only in the last scans. Conclusion: The O/E LHR is a good predictor of perinatal death in fetuses with left isolated CDH. Approximately 75% of fetuses at risk of perinatal death can be identified with an O/E LHR <= 35%, and 90% of them will have similar O/E LHR values at the first and at the last ultrasound examinations prior to delivery.