Studies on serum apolipoproteins and lipids in amniotic fluid and neonatal urine.

Amniotic fluid and neonatal urine were examined for the presence of lipids and serum apolipoproteins. Human apolipoproteins A-I, A-II, and ApoD found principally in serum high density lipoproteins were identified in both neonatal urine and amniotic fluid. A lecithin/sphingomyelin ratio of greater than 5 associated with fetal lung maturity was accompanied by the disappearance of A-II from amniotic fluid. Dissimilarities of total fatty acid composition of amniotic fluid when compared to cord serum or neonatal urine indicate other tissue sources for fatty acids found in amniotic fluid. In addition, the presence of serum apolipoproteins and lipids in both amniotic fluid and neonatal urine suggests that a least a portion of these constituents could be derived from fetal urine.