Use of the drop volume of amniotic fluid in estimating the risk for respiratory distress syndrome in the newborn infant.

The present study describes the testing and function of the drop-volume method in the analysis of fetal lung maturity with use of amniotic fluid. Elevated surface tension resulting from a lack of surface-active phospholipids (surfactant) is the primary etiologic defect in the development of respiratory distress syndrome. The drop-volume method quantifies the surface tension of amniotic fluid with use of the fact that the volume of a falling drop of liquid is proportional to the quantity of surfactant in the solution. The drop-volume method requires only 2 minutes and 2 ml of amniotic fluid and predicts fetal lung maturity with an accuracy equal to or greater than that of other tests currently in use.