Introduction Congenital diaphragmatic hernia (CDH) has an incidence of 1 in 2500 and around 30% of babies with isolated CDH die from pulmonary hypoplasia. There have been several techniques describing prediction of postnatal outcome in antenatally diagnosed isolated CDH based on the estimation of residual lung capacity by US and MRI. Recently, the observed to expected lung head ratio (O/E LHR) has been validated as a reliable method of lung estimation by 2D ultrasound and is a marker of postnatal morbidity and mortality.1 The authors sought to determine if the O/E LHR predicts survival in our West of Scotland population.

Methods The authors conducted a retrospective analysis of antenatally diagnosed isolated left-sided CDH cases referred to the Ian Donald Fetal Medicine unit, Queen Mother's Hospital, Glasgow from 2002 to 2009.

Results 58 patients had an antenatal diagnosis of isolated fetal left-sided CDH, lung head ratios were available for 25 cases. The mortality was 29%, none of these patients underwent in utero fetal tracheal occlusion. There was no significant difference in conventional LHRs between the neonates that survived (n=18) and those that did not (n=7), p=0.11. Using the O/E LHRs however the neonates that survived had a significantly higher O/E ratio than those that did not (p=0.03). The liver position (being in the fetal chest or abdomen) did not affect the O/E ratios in the group of survivors (p=0.26) or non-survivors (p=0.44).

Conclusion The authors have shown that the O/E LHR is a good predictor of mortality in our population of antenatally diagnosed CDH.