Determination of amniotic fluid palmitic acid concentration for the estimation of fetal lung maturity.

Palmitic acid concentrations in amniotic fluid (AF) were determined in 135 patients with normal and pathological pregnancies between the 27th and 42nd week of gestation. There was a sharp rise in the mean palmitic acid concentration after the 34th weeks of gestation from 2.7 mug/ml to 9.9 mug/ml at term. This increase is almost identical with the rise of AF-lecithin. It was found that between 70% and 100% of AF-palmitic acid originates from lecithin. 65 patients were delivered within 24 h after amniotic fluid sampling. 7 infants of these patients developed a respiratory distress syndrome (RDS). In all cases with RDS AF-palmitic acid concentration was far below 5 mug/ml. Assuming an AF-palmitic acid concentration greater than 5 mug/ml for characterising fetal lung maturity (=no RDS), there were no false negative results, but 16% false positive results. However, the determination of AF-palmitic acid concentration seems to be a most reliable method for the assessment of fetal lung maturity.