title: The acetone precipitation step is needed in determining the lecithin/ sphingomyelin (LS) ratio of amniotic fluid.
mesh_terms: D000653:Amniotic Fluid / Q000032:analysis*; D005325:Fetal Organ Maturity; D006801:Humans; D008168:Lung / Q000196:embryology; D010713:Phosphatidylcholines / Q000032:analysis*; D013109:Sphingomyelins / Q000032:analysis*
chemical_list: D010713:Phosphatidylcholines; D013109:Sphingomyelins