[Enzymic determination of dipalmitoylphosphatidylcholine in human amnionic fluid--its application for the judgement of fetal lung maturity before birth (author's transl)].

Respiratory distress syndrome (RDS) is believed to be caused by a deficiency of pulmonary surfactant. The surfactant, secreted by fetal lung into amnionic fluid, has been analyzed by a variety of methods, but none of these methods have been found accurate enough to be widely used. Dipalmitoylphosphatidylcholine (DP-PC), the major surface-active component of the surfactant, occupies more than 50% of the surfactant phospholipids. In this study, DP-PC isolated from amnionic fluid, was determined enzymatically. DP-PC started to increase gradually in amnionic fluid from 22nd week of gestation, showed rather rapid increase after 35th week of pregnancy, and reached to a value of 6.97 +/- 0.56 mg/dl (Mean +/- SEM, n = 117) between 38 and 42nd week of gestation. This increase of DP-PC during gestation was found to be quite similar to that of L/S ratio reported previously. Eight out of 10 infants with RDS had less than 1.0 mg/dl of DP-PC in the amnionic fluid, whereas 137 infants without any sign of RDS had more than 1.0 mg/dl of DP-PC except 5 cases. These results demonstrated that if more than 1.0 mg/dl of DP-PC was found in amnionic fluid before birth, the fetus could be judged to have mature lung with 96% accuracy. In addition the enzymic determination of DP-PC requires less time, rather easy and reliable method to be done in most general clinical laboratories with less cost. Therefore we believe this method will be widely used in near future for the detection of RDS before birth.