Urinalysis and Body Fluids 6th Edition by Majorie DiLorenzo, Susan Strasinger

Exercise 35

Explain the physiologic significance of the lecithinsphingomyelin (L/S) ratio.

Step 1 of 2

Lecithin-Sphingomyelin (L/S) ratio:

The Lecithin-Sphingomyelin ratio is the reference method that is used to compare the tests of FLM (Fetal Lung Maturity).

• The primary component of the surfactants (combination of phospholipids, proteins, and neutral lipids) is the lecithin ,which is helpful for stability of alveoli present in lungs

• Lecithin is produced constantly at low rate until 35^th week of gestation

• Sphingomyelin is a lipid produced constantly at low rate until 26^th week of gestation

• Both sphingomyelin and lecithin appears in amniotic fluid proportional to their concentrations in fetus

• After 35 weeks’ of gestation, lecithin production is elevated, whereas concentration of sphingomyelin remains constant