L/S ratio and the "G-force" factor.
D000653:Amniotic Fluid / Q000032:analysis*; D002498:Centrifugation; D006112:Gravitation; D006801:Humans; D010713:Phosphatidylcholines / Q000032:analysis*; D013109:Sphingomyelins / Q000032:analysis*
D010713:Phosphatidylcholines; D013109:Sphingomyelins