[Evaluation of P/S ratio and surface-tension measurements in amniotic fluid for prediction of pulmonary fetal maturity (author's transl)].

For the prediction of fetal lung maturity the palmitin stearic acid quotient (P/S ratio) was obtained by amniocentesis from 83 amniotic fluid samples of normal pregnancies, between the 28th and 40th week of pregnancy. This ratio was compared with the surface characteristics of the amniotic fluid in the Wilhelmy balance. A significant correlation was established between these two methods (correlation ellipsis r = 0.82, p < 0.01). The P/S ratio curve showed a marked increase during the 32nd and 36th week of pregnancy, indicating lung maturity. The P/S > 3 value usually reached during the 35th week of pregnancy indicates lung maturity. During the same time amniotic fluid samples were also obtained by amniocentesis from 37 complicated pregnancies. The surface tension as well as the P/S ratio were compared with the already established normal curves. A deceleration was found in cases of rhesusincompatibility and diabetes mellitus. In patients with EPH-gestosis and placental insufficiency only a slight acceleration towards the end of pregnancy was observed. Statistical proof of these trends was not feasible due to the limited number of patients in each group. Comparing the two methods regarding the predictability of pulmonary function in infants, the P/S ratio showed a larger number of false positive findings than the surface tension measurement method. Both methods produced an equal number of false negatives. Optimum results can be obtained by combining P/S ratio and surface tension measurements. This procedure is prognostically accurate in more than 96% of all cases.