Significance of amniotic fluid phospholipid determination for the prediction of neonatal respiratory distress syndrome.

198 amniotic fluid samples, obtained from 14-42 weeks of 158 patients were assessed for amniotic fluid phospholipids (total phospholipids, lecithin, sphingomyelin, lecithin/sphingomyelin ratio). The TPLP and Lec-concentrations show significant rises in concentration after 34th week whereas the sphingomyelin concentration remains virtually constant during pregnancy. L/S ratio remains relatively constant smaller than or equal to 2 prior to 32 weeks and smaller than or equal to 3 between 32 and 34 weeks but shows then a steep rise. The amount of Lec (expressed as percentage of total phospholipid concentration) rises from 30-40% at 30 weeks to 70-80% at term whereas the amount of Sph declines from 30-40% to less than 10%. In 12 cases neonatal RDS occurred. With L/S ratio treshold values of 3 correct prediction of RDS was made in 83% of cases, whereas probability of RDS occurrence was 63%. With L/S ratio values greater 3 RDS can be excluded in 95% of cases. The corresponding figures for Lec and TPLP concentration are described too. The range of different results in the literature is discussed.