Assessment of fetal pulmonary maturity by phospholipid analysis of amniotic fluid lamellar bodies

Lamellar inclusion bodies, when present in amniotic fluid, can be quantitatively harvested as a 10,000 x g pellet fraction. Phospholipid analysis of this fraction obtained from human amniotic fluid at various gestational ages revealed a developmental profile which correlated with individual stages in fetal pulmonary maturation. A presurfactant stage (i.e., indicating that the fetal lung has not yet begun to secrete surfactant), the first appearance of lamellar bodies in amniotic fluid, and the accumulation and biochemical maturation of lamellar bodies (as indicated by the appearance and accumulation of phosphatidylglycerol [PG]) were identified by the phospholipid composition of this fraction. Further investigations indicated that the earlier stages of development could be identified simply by measurement of the lecithin content of this fraction, and later stages, by the presence of PG. Since lecithin consistently represented 80% of the total phospholipids when PG was present, this factor could be accurately used in estimating the percentage of PG from the measurement of lecithin and PG alone.