Object ive : To evaluate the influence of amniocentesis to umbilical blood flow. To compare any difference between transamnionic and transplacental amniocentesis at midtrimester pregnancy Mehods : The doppler examination of umbilical cord was done before and after amniocentesis and fetal heart beat was checked from Jan. 1999 to Aug. 1999. We compared 20 cases of transplacental and 28 cases of transamnionic procedure. Comparision of data was done by student-t test and Paired t test. Res ult s : The pulsatility index(PI) in the umbilical artery was decreased more at the transplacental than at the transamnionic procedure, but there was no statistical significance.(p>0.05). Fetal heart beat was increased about 1.5 after amniocentesis. Conclus ion : We believe the human placenta has some compensatory mechanism respond stress such as amniocentesis.

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