Determination of fetal lung maturity by fluorescence polarization of the amniotic fluid lamellar bodies

High-speed centrifugation of amniotic fluid enables separation of surfactant-containing lamellar bodies. Fifty-three amniotic fluid samples from pregnancies of 28 to 39 weeks' gestation were examined for fetal lung maturity by measuring fluorescence polarization (P). For each sample the P value was determined at 37% on both the whole amniotic fluid and on the surfactant-containing lamellar bodies obtained by centrifugation at 10,000 x g. A close linear correlation (r = 0.80) was found between the P value of the amniotic fluid samples and that of the lamellar bodies. There was no difference in the specificity for discrimination of hyaline membrane disease cases by both methods (93.5%) with 95% confidence limits of 82.1 to 98.6%. Because highspeed centrifugation enables the selective sedimentation of pulmonary surfactant, determination of the lamellar body P value may offer a practical solution for the estimation of fetal lung maturity in amniotic fluid samples contaminated with blood.