Clinical Utility of Fetal Lung Maturity Profile

The usefulness of the lung maturity profile in predicting the absence of respiratory distress syndrome (RDS) in the newborn was assessed in 356 patients with an obstetric indication for amniocentesis. Newborn infants delivered of mothers with a lecithinsphingomyelin (L:S) ratio greater than 2.0, phosphatidylinositol at a level indicating maturity, and phosphatidylglycerol greater than 2% experienced no RDS. Twenty-six of 40 patients with studies indicating immaturity, in contrast, experienced RDS. Similarly, 20 infants who were predicted to be mature by L:S ratio but in whom no phosphatidylglycerol was present experienced a 40% incidence of RDS. In a small number of patients in whom the L:S ratio suggested that the fetal lung was immature, but in whom the phosphatidylglycerol level was greater than 2%, no RDS occurred. These results suggest that a mature lung profile is more valuable in predicting absence of RDS in the newborn than the L:S ratio alone. Certain conditions known to be associated with a mature L:S ratio but associated with development of RDS in the newborn may be more accurately assessed by the presence or absence of phosphatidylglycerol in amniotic fluid. Although the series is small, it appears that the presence of phosphatidylglycerol even with an immature L:S ratio predicts that the newborn will be free of RDS.