title: Letter: Respiratory maturity in infants.
mesh_terms: D000653:Amniotic Fluid / Q000032:analysis* / Q000166:cytology; D005314:Embryonic and Fetal Development; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000175:diagnosis*; D010713:Phosphatidylcholines / Q000032:analysis; D011247:Pregnancy; D012131:Respiratory Insufficiency / Q000175:diagnosis*; D013109:Sphingomyelins / Q000032:analysis
chemical_list: D010713:Phosphatidylcholines; D013109:Sphingomyelins