Lecithin-sphingomyelin (L/S) ratio - amniotic fluid

Last updated: Thursday, 22, April, 2004

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Item Process

Amniotic fluid.

MethodThin layer chromatography. Some laboratories also measure phosphatidyl glycerol or count lamellar bodies.
Reference Interval

L/S ratio >2.0 indicates fetal lung maturity.


Assessment of foetal lung maturity.

See also Phosphatidyl glycerol - amniotic fluid and Lamellar bodies - amniotic fluid.


L/S ratio <2.0 indicates an increased risk of respiratory distress syndrome (RDS) at delivery.

L/S ratio <1.5 indicates a very high risk of developing RDS.

Babies of diabetic mothers can develop RDS with L/S ratios >2.0.

ReferenceSpillman T and Cotton DB. Crit Rev Clin Lab Sci 1989; 27: 341-389.