Fetal lung volume measurement by magnetic resonance imaging in congenital diaphragmatic hernia

Abstract

Objective To study the potential for prenatal magnetic resonance imaging to predict pulmonary hypoplasia in congenital diaphragmatic hernia. Design Prospective observational study. Setting Tertiary care centre. Participants Thirteen cases of congenital diaphragmatic hernia (11 left, 2 right) without associated anomalies and 74 controls. Methods Measurements by magnetic resonance imaging of fetal lung volume were achieved. In the control fetuses, a regression analysis was performed to associate fetal lung volume with gestational age. This yielded a formula allowing calculation of the expected fetal lung volume as a function of gestational age. In the cases with congenital diaphragmatic hernia, the observed/expected fetal lung volume ratio was compared with perinatal outcome. Main outcome measures Neonatal mortality and pulmonary hypoplasia, which was defined as lung/body weight ratios less than 0.012. Results The expected fetal lung volume was derived from the following formula: Fetal lung volume (mL) = exp (1.24722 + 0.08939 × gestational age in weeks). The observed/expected fetal lung volume ratio was significantly lower in congenital diaphragmatic hernia (median: 0.31, range: 0.06–0.63), than in controls (median: 0.99, range: 0.42–1.94). This ratio was significantly less in the infants with congenital diaphragmatic hernia who died (median: 0.26, range: 0.06–0.63) compared with those who survived (median: 0.46, range: 0.35–0.56). The observed: expected fetal lung volume ratio was significantly correlated with the post mortem lung: body weight ratio. Conclusion In isolated congenital diaphragmatic hernia, fetal lung volume measurement by magnetic resonance imaging is a potential predictor of pulmonary hypoplasia and postnatal outcome. Further studies are required to establish the clinical value of magnetic resonance imaging for the prenatal assessment of fetal lungs.