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 lu ng measurements for the prediction of severe fetal pulmonary hypoplasia in congenital diaphragmatic hernia and to determine whether a correlation betw een lung measurements and autopsy findings or neonatal outcome could be est ablished. Design Prospective study, between 1991 and 1997. Subjects Nineteen fetuses with congenital diaphragmatic hernia. Methods In addition to standard biometry sonographic measurement of the tra nsverse thoracic diameter, sagittal thoracic diameter, fetal lung diameters at the level of the four-chamber view and lung/thoracic circumference rati o were performed. These were compared with the standard curves defined by M erz and colleagues. Autopsy examinations were performed to determine lung w eight, lung weight/body weight ratio and radial alveolar count. Results Five fetuses (26%) were terminated before 24 weeks of gestation. Al l of these fetuses had lung measurement values below the 5th centile. Eleve n 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 fet uses without associated anomalies. The sonographic diagnosis of fetal pulmo nary hypoplasia was made in all fetuses who died postnatally. All fetuses w ith a lung diameter/thoracic circumference ratio below 0.09 died. Three fet uses, which had values within the nor mal range, survived. In contrast, mea surements of the bony thorax (transverse and sagittal thoracic diameters, t horacic circumference) did not provide an indication of the presence of fet al pulmonary hypoplasia. Pulmonary hypoplasia was confirmed at autopsy in a ll fetuses on the basis of lung weight, lung/body weight ratio or radial al veolar count. Concomitant with pulmonary hypoplasia was polyhydramnios in t en fetuses (71.4%), mediastinal shift in 11 fetuses (78.6%), intrathoracic herniated stomach in six fetuses (42.9%) and associated malformations in fo ur 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 circumferenc e ratio are further useful prognostic pai parameters in the management of c ongenital diaphragmatic hernia.