[Enzymatic determination of lecithin concentration in the amniotic fluid for antepartal determination of fetal lung maturity].

An enzymatic method of determining the lecithin concentration in the amniotic fluid is compared with the present standard method of antepartal determination of fetal lung maturity, i.e., determination of the lecithin-sphingomyelin (L/S) ratio. A total of 320 amniotic fluid samples, of which 154 were obtained within the 72 hours preceding birth, were studied by both methods. Simultaneously with the rise in the L/S ratio in the amniotic fluid there is a rise in the enzymatically determined lecithin concentration in the last quarter of pregnancy. The critical threshold value for RDS risk of 2 for the L/S ratio corresponds to a threshold value of 5 mg/100 ml amniotic fluid for the enzymatically analyzed lecithin concentration. Established lung maturity can be demonstrated with the same degree of confidence as by using the L/S ratio. The specificity of the both methods is 91%. It is at least as easily possible to predict the likelihood of respiratory distress syndrome by determining the enzymatic lecithin concentration (11 out of 15 cases) as by means of the L/S ratio (9 out of 15). In order to improve the sensitivity (L/S ratio 60%, enzymatic lecithin determination 73%) it would be necessary to perform an additional analysis-e.g., of phosphatidylglycerol-in the amniotic fluid.