The ultrasonographic assessment of the fetal thorax and fetal breathing movements in the prediction of pulmonary hypoplasia.

Comparison was made of fetal breathing movements (FBM) and thoracic measurements in the prenatal diagnosis of pulmonary hypoplasia. In 20 pregnancies with oligohydramnios due to premature and prolonged rupture of the membranes (PROM) the presence or absence of FBM was assessed, the internal thoracic and cardiac circumferences were measured and the internal thoracic and lung areas calculated. All 5 infants with absent FBM died from pulmonary hypoplasia in the neonatal period and all 15 with FBM present survived. The internal thoracic circumference of 3 of the fetuses that developed pulmonary hypoplasia and 1 of those that did not were below the 2.5th centile of a reference range constructed from 76 normal pregnancies. Similarly, the lung areas were below the 2.5th centile of our reference range in 3 fetuses who developed pulmonary hypoplasia and 2 of those that survived. The absence of FBM was found to be the most accurate predictor of pulmonary hypoplasia in pregnancies complicated by oligohydramnios due to PROM.