The amount of total lipids of the amniotic fluid of normal human subjects increases progressively with gestational age and is found to be maximum in labor at term. The Iecitbin/sphingomyelin ratio, which invariably increases with gestational age, is 2:1 or greater beyond 34 weeks of pregnancy and becomes maximum at term labor. No definite correlation exists between the palmitic acid content of total lipids and gestational age; but the palmitic acid content of the lecithin fraction increases with gestational age and this increase is markedly accelerated near the 34th week of pregnancy. Also it is observed that the arachidonic acid of cholesterol esters increases with gestational age. Therefore, it is suggested that both the palmitic acid level of lecithin and the arachidonic acid level of cholesterol esters might serve as more reliable indices than current methods being employed for the assessment of fetal lung maturity.
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