Factors Influencing the Measurement of the Lecithin/Sphingomyelin Ratio in Amniotic Fluid

Summary The estimation of the lecithin/sphingomyelin (L/S) ratio of amniotic fluid is a valuable aid in determining the optimum time for delivery in complicated pregnancies. The method of Borer and Gluck (1971) has been widely adopted because of its simplicity, the use of commercial chromatogram material, and the need for only small quantities of amniotic fluid. While the actual values reported originally have usually been adopted in clinical management, the technique has frequently been modified by following workers in ways that may radically alter the final result. The effects on the L/S ratio and the physical determination of surfactant of changes in the method and the presence in the amniotic fluid of chemical or biological contaminants have been measured and assessed.