Lecithin-sphingomyelin ratio - AbsoluteAstronomy.com

The lecithin-sphingomyelin ratio is a test of fetal amniotic fluid

Amniotic fluid

Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...

to assess for fetal lung immaturity. Lungs require surfactant

Surfactant

Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...

, a soap-like substance, to lower the surface pressure of the alveoli in the lungs. This is especially important for premature babies trying to expand their lungs after birth. Surfactant is a mixture of lipids, proteins, and glycoproteins, lecithin

Lecithin

Lecithin is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues, and in egg yolk, composed of phosphoric acid, choline, fatty acids, glycerol, glycolipids, triglycerides, and phospholipids .The word lecithin was originally coined in 1847 by...

and sphingomyelin

Sphingomyelin

Sphingomyelin is a type of sphingolipid found in animal cell membranes, especially in the membranous myelin sheath that surrounds some nerve cell axons. It usually consists of phosphorylcholine and ceramide...

being two of them. Lecithin makes the surfactant mixture more effective.

Evaluation

As the lungs mature and become better able to produce surfactant, the ratio of lecithin to sphingomyelin increases in the amniotic fluid. As such, if a sample of amniotic fluid has a higher ratio, it indicates that there is more surfactant in the lungs and the baby will have less difficulty breathing at birth. An L/S ratio of 2 or more indicates a relatively low risk of infant respiratory distress syndrome

Infant respiratory distress syndrome

Infant respiratory distress syndrome , also called neonatal respiratory distress syndrome or respiratory distress syndrome of newborn, previously called hyaline membrane disease, is a syndrome in premature infants caused by developmental insufficiency of surfactant production and structural...

, and an L/S ratio of less than 1.5 is associated with a high risk of infant respiratory distress syndrome.

If preterm delivery is necessary (as evaluated by a biophysical profile

Biophysical profile

A biophysical profile is a prenatal ultrasound evaluation of fetal well-being, involving a scoring system. It is often done when a non-stress test is non reactive, or for other obstetrical indications.-The test:...

or other tests) and the L/S ratio is low, the mother may need to receive steroids to hasten the fetus' surfactant production.

Procedure

An amniotic fluid sample is collected via amniocentesis

Amniocentesis

Amniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for...

and the sample is spun down in a centrifuge

Centrifuge

A centrifuge is a piece of equipment, generally driven by an electric motor , that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis...

at 1000 rpm for 3 to 5 minutes. Thin layer chromatography

Thin layer chromatography

Thin layer chromatography is a chromatography technique used to separate mixtures. Thin layer chromatography is performed on a sheet of glass, plastic, or aluminum foil, which is coated with a thin layer of adsorbent material, usually silica gel, aluminium oxide, or cellulose...

(TLC) is performed on the supernatant, which separates out the components. Lecithin and sphingomyelin are relatively easy to identify on TLC and the predictive value of the test is good.

Evaluation

Procedure

See also