Phospholipids in Amniotic Fluid

. Amniotic fluid samples were extracted with chloroform and methanol for lipids. Thin layer chromatography (TLC) was used to separate the phospholipids. Lecithin spots from the TLC were scraped and methylated for fatty acid (FA) analysis by gas liquid chromatography (GLC). The FA composition of the lecithins from 61 samples of amniotic fluid were determined. These included 17 from diabetic mothers, 36 from Rh sensitized mothers and 8 from normal or pre‐eclamptic mothers at gestational ages from 26–42 weeks. The percentage of saturated FA increased from 58–70% at gestational ages of 26–31 weeks to 75–90% after 37 weeks gestation. Palmitic acid comprised 24–51%, myristic acid 0–4%, stearic acid 18–44% and oleic acid 16–32% of the lecithin FA between 26–31 weeks gestation. With increasing gestational age, the percentage of palmitic and myristic acids increased, while the percentage of stearic and oleic acid decreased. Five of 27 infants, delivered within seven days of obtaining the amniotic fluid samples and between 24–42 weeks gestation, developed RDS. The lecithins from the five patients with RDS had no myristic acid and decreased palmitic acid (4 of 5<60%) compared with healthy infants of similar gestational age. The amniotic fluid lecithin from the five infants with RDS had 16–35% stearic acid while only two of 22 healthy infants had >9% stearic acid (11 & 17%). The ratio of stearic acid to oleic acid (SA/OA) was >1.3 in all five infants with RDS, and <1.3 in all healthy infants. Amniotic fluid from infants born between 34 and 38 weeks gestation who develop RDS has not only decreased. Five of 27 infants, delivered within seven days characteristic FA patterns associated with decreased surfactant activity. The percentage of stearic acid more closely parallels pulmonary maturity than the concentration of lecithin or the L/S ratio.