• E Ryo, T Okai, S Kozuma, K Kobayashi, A Kikuchi, and Y Taketani.
• Department of Obstetrics and Gynecology, Faculty of Medicine, University of Tokyo, Japan.
• Int J Gynaecol Obstet. 1996 Dec 1;55(3):213-8.

ObjectiveTo evaluate the inferior vena cava compression and its influence on the uterine and umbilical artery blood flow in the late second trimester when the mother is supine.MethodsThe inferior vena cava diameter was measured by ultrasound B mode scan, and Doppler flow velocimetry of the uterine and umbilical artery was performed in 90 women at 24-27 weeks in the supine and complete left lateral position.ResultsThe inferior vena cava diameter in the supine position was significantly smaller than that in the lateral position. The degree of the vena cava compression was associated with an elevation in the uterine artery RI in the supine position. The umbilical artery RI did not couple with either the degree of the compression or the changes in the uterine artery RI.ConclusionThe inferior vena cava is compressed in the majority of pregnant women in the second trimester, and the compression may affect the uterine artery blood flow but not the fetal circulation.

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