[Comparison of surface tension with determination of the L/S ratio in amniotic fluid for prediction of fetal lung maturity].

In 83 specimen of amniotic fluid both a dynamic measurement of the surface tension by the Wilhelmy-balance and a determination of the lecithin-sphingomyelin-ratio were performed in 1987-1992 in order to predict a respiratory-distress-syndrome (RDS) of the newborn. 7 cases showed divergent results of both methods. In comparison with the measurement of surface tension by the Wilhelmy-balance, determination of the lecithin/sphingomyelin-ratio showed more false positive results (4:1). Both methods provided false negative results in two cases each. In two cases both methods showed false positive results, with RDS occurring in spite of predicted lung maturity. In our high risk-collective 5 of 83 newborns developed a severe RDS. All of them were delivered by caesarean section. A secondary deficiency of surfactant as a result of fetal hypoxia or acidosis as well as a possible influence of the way of delivery might be responsible for the development of RDS. The Wilhelmy-balance, which can be used as a bed-side-method, provides similar results in the prediction of fetal lung maturity compared to the L/S-ratio.