[Surface tension properties of the amniotic fluid obtained by serial puncture in normal pregnancies (author's...

Serial amniotic fluid samples were obtained in the last trimester of pregnancy during the course of 12 uneventful pregnancies. The surface tension properties of the amniotic fluid samples were measured in the surface (Wilhelmy) balance. Eight pregnancies showed a normal pattern of surface activity parameters, whereas in four pregnancies the pattern was abnormal. The pattern of surface activity parameters is shown individually for each of the 12 pregnancies and the possible reasons for individual variations are discussed.