Comparison of Amniotic Fluid Disaturated Phosphatidylcholine and the Lecithin- Sphingomyelin Ratio in the Prediction of Fetal Lung Maturity

Although use of the lecithin-sphingomyelin (L/S) ratio has contributed to a reduction in the frequency of respiratory distress syndrome (RDS), its accuracy in pregnancies complicated by fetomaternal disease has been questioned. Disaturated phosphatidylcholine is the major active component of surfactant and has been advocated as being a more specific indicator of fetal lung maturity. A study of 105 pregnancies in which a L/S ratio and disaturated phosphatidylcholine assay were performed on amniotic fluid was carried out to ascertain if amniotic fluid disaturated phosphatidylcholine is indeed a more accurate predictor of RDS. The results of this investigation reveal no significant difference in the reliability of these two tests in predicting neonatal RDS. Five infants developed RDS with a mature L/S ratio ranging from 2.0 to 3.36, suggesting that the disaturated phosphatidylcholine assay may be a helpful adjunctive test in instances in which the L/S ratio is less than 3.5.