Correlation between amniotic fluid optical density, L/S ratio, and fetal pulmonary maturity.

The correlation between lecithin/sphyngomyelin ratio (L/S ratio) and amniotic fluid optical density at 400 (OD400) and 650 (OD650) nm was studied with 102 samples of fluid obtained from 72 patients. The accuracy of each method in predicting the respiratory outcome of the newborn was also evaluated in 28 patients who delivered within 48 hours after amniocentesis. Results indicate that the correlation between spectrophotometric analysis and L/S ratio is poor and that the latter is a better predictor of neonatal respiratory outcome. It is concluded that measurements of amniotic fluid optical density are not an acceptable substitute for the L/S ratio in evaluating fetal pulmonary maturity.