In addition to lecithin, the other phospholipids in the amniotic fluid increase as the fetus reaches term. The presence of phosphatidylglycerol (PG) and phosphatidylinositol are associated with fetal lung maturity as they help maintain alveolar stability. Phosphatidylglycerol appears around 36 weeks of gestation.


Specimen: Amniotic fluid, protected from light


Testing Methods: Phospholipids can be measured using thin layer chromatography, enzymatically or by agglutination methods.



• phosphatidylglycerol > 2 µmol/L or > 2% of total phospholipid ("positive" or "present"): indicates fetal maturity

• phosphatidylinositol > 15% of total phospholipid ("positive" or "present"): indicates fetal maturity

• the presence of phosphatidylglycerol has a high predictive value of no respiratory distress in the infant

• the absence of phosphatidylglycerol can have a low predictive value for occurrence of respiratory distress (depending on population studied), resulting in a high false immaturity rate


Interferences: Not affected by many of the disorders limiting the L/S ratio (maternal diabetes mellitus, erythroblastosis fetalis, contaminants in amniotic fluid)


To read more or access our algorithms and calculators, please log in or register.