Foam-stability test on gastric aspirate and the diagnosis of respiratory-distress syndrome.

Gastric aspirate, collected from 79 infants within 30 minutes of birth, was subjected to the foam-stability test. The lecithin/sphingomyelin ratio was determined in 27. The results were compared with the incidence of respiratory-distress syndrome as determined independently by different investigators. Of the 59 infants with a positive foam-stability test on gastric aspirate, three had transient respiratory distress, and one the respiratory-distress syndrome; 17 of 22 had lecithin/sphingomyelin ratios greater than 2.0. Of nine infants who had intermediate test results, three were normal, four had transient respiratory distress, and two had the respiratory-distress syndrome. In all the 11 infants with negative foam-stability tests the respiratory-distress syndrome developed. The three gastric aspirates tested in this group had lecithin/sphingomyelin ratios of less than 1.5. These data indicate that the foam-stability test on gastric aspirate is a reliable index of fetal lung maturity in infants whose amniotic fluid is not available.