Cholesteryl palmitate as a predictor of fetal lung maturity.

Cholesteryl palmitate was measured by thin-layer chromatography in 98 amniotic fluid samples obtained from pregnancies ranging from 15 to 40 weeks. Pregnancies complicated by diabetes mellitus or Rh sensitization were excluded. Cholesteryl palmitate concentration increased with gestational age from values less than 5 micrograms/ml at 15 weeks to maximum values of 384 micrograms/ml at term. Seventy-three patients were delivered of their infants within 24 hours of sampling. The mean concentration of cholesteryl palmitate for 55 infants without respiratory distress syndrome was 123.70 +/- 12.21 micrograms/ml (SD). For neonates that developed respiratory distress syndrome (n = 18), the mean concentration was 22.66 +/- 6.16 micrograms/ml (SD). This difference is significant (p less than 0.001). For all patients delivered, respiratory distress syndrome was not seen when the cholesteryl palmitate concentration was greater than 41 micrograms/ml (mean + 3 SD). All infants with a concentration below 38 micrograms/ml developed respiratory distress syndrome. We conclude that measurement of cholesteryl palmitate concentration in amniotic fluid might be another reliable method of assessing fetal lung maturity and may often improve specificity when compared with other tests of fetal lung maturity.