[The value of various investigations of amniotic fluid in the estimation of fetal maturity (author's transl)].

The amniotic fluid lecithin-spingomyelin (L/S) ratio, creatinine and uric acid concentrations, percentage of organe-stained fat cells and the foam test by Clements and coworkers have been compared in 82 samples of amniotic fluid from 66 patients. The specimens were obtained by transabdominal amniocentesis or amniotomy between the 24th and the 42nd week of pregnancy. The determination of the L/S ratio and the foam test seem to be reliable methods of estimating pulmonary surfactant and, hence, of predicting the respiratory distress syndrome (RDS) in the newborn infant. There was no RDS with an L/S ratio greater than 1.6 to 1.8. Positive foam tests also seem to be a valuable indicator of pulmonary maturity, no cases of RDS being found. However, false negative foam tests are not rare. The amniotic fluid concentration of creatinine correlated well with gestational age and birth weight. The determination of uric acid in the amniotic fluid is an unreliable test of fetal maturity on account of the large scatter. The percentage of orange-stained cells did not rise above 10% before the 39th week of pregnancy in most cases.