The sonographic features and implications of fetal pleural effusions

Pleural fluid was detected by ultrasound in three fetuses as an anechoic area surrounding the echogenic fetal lung. In one fetus the underlying lung was small, immobile and of abnormal contour; death occurred in the neonatal period and the lung was found to be hypoplastic. In two other fetuses the lungs appeared sonographically normal, being mobile with normal contours. Both survived, one following spontaneous intra-uterine resolution of the effusion and the other after early neonatal intervention prompted by the antenatal diagnosis. Sonography can detect pleural fluid in utero and may permit differentiation between normal underlying lung and pulmonary hypoplasia. We recommend serial scanning to detect early adverse effects of pleural effusion upon the fetus and to plan management changes.