Comparison of amniotic fluid optical density and foam stability test in predicting fetal lung maturity.

The ability of optical density measurements and the foam stability test to predict the L/S ratio of amniotic fluid (AF) was examined. Optical density measurements and the foam test predicted the L/S ratio with a similar degree of accuracy; neither was able to replace biochemical measurement of the L/S ratio because both gave false negative and false positive predictions. Optical density measurements and the foam test did not combine to increase the accuracy of prediction.