A comparison between the lecithin/sphingomyelin ratio of Gluck and other phospholipid values of amniotic fluid.

We have found the lecithin/sphingomyelin ratio of Gluck (L/S ratio) to be very useful for predicting respiratory distress. It correlated reasonably well with three other phospholipid values: the total lecithin content, the acetone-insoluble lecithin content, and the total lecithin/total phospholipids ratio. When the L/S ratio of amniotic fluid was greater than 2.0 there was no respiratory distress, even if the other phospholipid values indicated that the fetal lungs were still immature.