Amniotic fluid
cholesteryl palmitate, as measured by thin-layer chromatography, appears to be a very sensitive and specific predictor for the risk of
respiratory distress syndrome (RDS) in newborns of normal pregnancies. To assess the effect of
diabetes mellitus on fetal pulmonary maturation, we measured
cholesteryl palmitate concentration, the lung profile, and total
phosphatidylcholine in amniotic fluid obtained from 35 well-controlled diabetic and 39 control pregnancies at term. In women with diabetes, the mean (+/- SD) third-trimester
glycosylated hemoglobin level was 6.96 +/- 2.3% (normal 6-8%). Mean
cholesteryl palmitate concentration in the diabetic population was 79.12 +/- 13.17 micrograms/mL, versus 153.71 +/- 16.77 micrograms/mL in the control group (P less than .001). The mean
cholesteryl palmitate concentration was also significantly different for gestational diabetics and class B-R gravidas (112.75 +/- 26.2 versus 54.45 +/- 7.34 micrograms/mL; P less than .005).
Cholesteryl palmitate was decreased despite the presence of a mature
lecithin/
sphingomyelin ratio and, in most cases,
phosphatidylglycerol. These data suggest that even in well-controlled diabetic pregnancies, alterations in maternal metabolism may affect either the biosynthesis or degradation of
cholesteryl palmitate.