Relationships among human amniotic fluid dipalmitoyl lecithin, postpartum respiratory compliance, and neonatal respiratory distress syndrome.

The major molecular species of amniotic fluid phosphatidylcholine were determined as diacylglycerol trimethylsilyl ether derivatives by gas-liquid chromatography with use of glass capillary columns. We studied amniotic fluid specimens from 48 pregnancies. As expected, the major disaturated species of amniotic fluid phosphatidylcholine, dipalmitoylphosphatidylcholine, and palmitoylmyristoylphosphatidylcholine increased with gestational age, whereas phosphatidylcholine species with 34, 36, and 38 carbon atoms in the acyl radicals decreased. Although the amniotic fluid samples were obtained shortly before parturition (4.2 +/- 3.7 h, mean +/- SD), the correlation between dipalmitoylphosphatidylcholine concentration in amniotic fluid and gestational age was better than between dipalmitoylphosphatidylcholine concentration and the compliance of the respiratory system of the newborns. In addition, the percentage of amniotic fluid phosphatidylcholine species present as dipalmitoylphosphatidylcholine seemed to be a more reliable predictor of lung maturity than was the absolute dipalmitoylphosphatidylcholine concentration in amniotic fluid.