Determination of lecithin and sphingomyelin in amniotic fluid (L/S ratio)

Determination of the ratio of lecithin to sphingomyelin (L/S ratio) in amniotic fluid is a viable method of monitoring and assessing fetal lung maturity. This is particularly important in high-risk pregnancies for which early confinement is to be expected or aimed at.
Chloroform extract of amniotic fluid is chromatographed on silica gel, derivatized with manganese (ll)-chloride – sulfuric acid reagent, and evaluated densitometrically by fluorescence measurement. The working range of this procedure is 5 – 50 mg/L.
The recovery rate (n=8) is determined to be 93% ± 1.5% for lecithin and 90% ± 2.0% for sphingomyelin.