Amniotic fluid cholesteryl palmitate in pregnancies complicated by diabetes mellitus.

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.