Congenital diaphragmatic hernia: ultrasonic measurement of fetal lungs to predict pulmonary hypoplasia.

OBJECTIVE

The purpose of this study was to assess the value of biometric lung measurements for the prediction of severe fetal pulmonary hypoplasia in congenital diaphragmatic hernia and to determine whether a correlation between lung measurements and autopsy findings or neonatal outcome could be established.

DESIGN

Prospective study, between 1991 and 1997.

SUBJECTS

Nineteen fetuses with congenital diaphragmatic hernia.

METHODS

In addition to standard biometry, sonographic measurement of the transverse thoracic diameter, sagittal thoracic diameter, fetal lung diameters at the level of the four-chamber view and lung/thoracic circumference ratio were performed. These were compared with the standard curves defined by Merz and colleagues. Autopsy examinations were performed to determine lung weight, lung weight/body weight ratio and radial alveolar count.

RESULTS

Five fetuses (26%) were terminated before 24 weeks of gestation. All of these fetuses had lung measurement values below the 5th centile. Eleven of 14 fetuses (78.6%) with pulmonary hypoplasia diagnosed after 24 weeks of gestation died postnatally. The mortality rate was 70% (7/10) in the fetuses without associated anomalies. The sonographic diagnosis of fetal pulmonary hypoplasia was made in all fetuses who died postnatally. All fetuses with a lung diameter/thoracic circumference ratio below 0.09 died. Three fetuses, which had values within the normal range, survived. In contrast, measurements of the bony thorax (transverse and sagittal thoracic diameters, thoracic circumference) did not provide an indication of the presence of fetal pulmonary hypoplasia. Pulmonary hypoplasia was confirmed at autopsy in all fetuses on the basis of lung weight, lung/body weight ratio or radial alveolar count. Concomitant with pulmonary hypoplasia was polyhydramnios in ten fetuses (71.4%), mediastinal shift in 11 fetuses (78.6%), intrathoracic herniated stomach in six fetuses (42.9%) and associated malformations in four fetuses (28.6%). Postnatal mortality for these conditions was 80%, 78.6%, 100% and 100%, respectively. Postnatal mortality was 75%, 70% and 100% in the fetuses with an isolated diaphragmatic hernia.

CONCLUSION

The results of this investigation suggest that the assessment of fetal lung diameter and the use of the lung diameter/thoracic circumference ratio are further useful prognostic parameters in the management of congenital diaphragmatic hernia.