title: Letter: Lecithin/sphingomyelin ratio in tracheal aspirate.
mesh_terms: D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007745:Labor Onset; D008168:Lung / Q000196:embryology; D010713:Phosphatidylcholines / Q000032:analysis*; D011247:Pregnancy; D012127:Respiratory Distress Syndrome, Newborn / Q000175:diagnosis; D013109:Sphingomyelins / Q000032:analysis*; D014132:Trachea
chemical_list: D010713:Phosphatidylcholines; D013109:Sphingomyelins