A calibrated fluorescence polarization assay for assessment of fetal lung maturity.

The mechanism of a new fluorescence polarization method for measuring phospholipid in amniotic fluid is described. The fluorescence polarization of a surfactant fluorescent dye solubilized in amniotic fluid correlates significantly with the L/S ratio. Model studies indicate that this results primarily from partitioning of the dye between endogenous albumin, which causes a high fluorescence polarization, and dispersed phospholipid, which causes a much lower polarization. The fluorescence polarization can be compared with a calibration curve to give the ratio of phospholipid to albumin in the sample. This procedure may prove useful in antenatal assessment of fetal lung maturity.