Reliability of the lung‐to‐head ratio in predicting outcome and neonatal ventilation parameters in fetuses with congenital diaphragmatic hernia

Abstract

The ratio of the lung area (on the contralateral side of the hernia) to the head circumference, the lung-to-head ratio (LHR), has been proposed as a reliable tool in the assessment of the prognosis of congenital diaphragmatic hernia (CDH). An LHR < 0.6 has been associated with poor outcome whereas one > 1.4 has been associated with survival. We aimed to analyze the role of LHR in predicting fetal outcome and ventilation parameters in cases of isolated CDH in our center. During the 40-month study period, 22 fetuses with an isolated CDH were delivered alive under optimized conditions at our perinatal center. LHR was measured at the time of diagnosis (median, 27 weeks' gestation). In addition to survival, postnatal ventilation parameters including pCO2, pO2, inspiratory O2 partial pressure, inspiratory pressure and oxygenation index were determined, as was the occurrence of pulmonary hypertension. The overall survival rate was 59%. The LHR was not able to predict fetal outcome reliably. There was no correlation between the liver herniation, LHR and fetal outcome. The prenatally determined lung size reflected in the LHR did not show any significant association with individual ventilation parameters. Eleven of 17 infants examined had signs of pulmonary hypertension and the LHR did not predict this condition. Our study cannot support the optimistic results reported by other groups on the use of LHR as a reliable predictor of outcome in fetuses with CDH. The LHR, as a reflection of lung size, correlates neither with survival patterns nor with various postnatal ventilation parameters.