[Evaluation of the lecithin/sphingomyelin ratio and the foam test as tests of fetal lung maturity].

The lecithin/sphingomyelin (L/S) ratio and the foam test to determine fetal lung maturity in order to prevent hyaline membrane disease (HMD) were used in 800 patients at Tygerberg Hospital. The incidence of HMD in all neonates diminished from 3.25% in 1971, when the lung maturity test was not done, to 2.12% in 1975, the 4th year that such determinations were done. In the same period the incidence of respiratory distress syndrome (RDS) increased from 3.68% to 4.31%. Only 1% of fetuses in whom lung maturity was determined during the period 1972--1975 developed HMD. This reduced incidence of HMD is considered to be the result of prenatal determination of fetal lung maturity. No correlation was found between fetal lung maturity and length of gestation or physical condition of the neonate. The foam test results were compared with the L/S ratio, and a false positive figure of 8.3% and a false negative figure of 27.1% were found. It is recommended that the foam test be used for screening and the L/S determination be done only if the foam test is negative in high-risk patients.