Comparison of four indexes to fetal pulmonary maturity.

With use of the same amniotic fluid specimens, lecithin concentration was compared with nonchromatographically determined glycerophospholipid, total lipid phosphorus, and the bubble-stability test as indexes of fetal lung maturation. The lecithin analysis was performed by thin-layer chromatography, with use of a semiautomated method of spotting and nondigestive release of phosphorus from the separated spots. We conclude that, next to the chromatographic analysis, the best tests are glycerophosphatide P, the bubble-stability test, and total lipid P, in that descending order. Lecithin determination as compared with densitometric evaluation of the lecithin/sphingomyelin ratio is discussed.