Surfactant "apoproteins" in human amniotic fluid: an enzyme-linked immunosorbent assay for the prenatal assessment of lung maturity.

We have developed an enzyme-linked immunosorbent assay for the quantitation of human lung surfactant high--molecular weight proteins and used this assay to evaluate changes in surfactant "apoprotein" content of amniotic fluid during the last trimester of pregnancy. The amount of surfactant apoprotein in human amniotic fluid increased with advancing gestational age and correlated well with other parameters of fetal lung maturity, the lecithin:sphingomyelin ratio, and the presence of phosphatidylglycerol. The findings suggest that this test, which is relatively simple to perform, may prove useful as an additional clinical parameter for assessing fetal lung maturity and predicting more accurately fetuses at risk of developing hyaline membrane disease.