Objective : Pregnancy is considered to increase the risk of deep vein thrombosis (DVT). However, it is not easy to detect women at higher risk of DVT before and after conception. Therefore, this study investigated physiological changes in the lower limbs during and after pregnancy as basic data to prevent DVT.
Material : One hundred and sixteen pregnant women and 10 non-pregnant women were investigated in the present study. One hundred twenty examinations were totally performed. Method : The diameter of vessels and blood flow velocity of the superficial femoral (FV) and popliteal vein (PV) in the bilateral limbs were measured with ultrasound in all cases. To assess the physiological changes during pregnancy, four periods during pregnancy were defined in the present study. These were between 6 and 10 weeks (early (e) stage), between 20 and 24 weeks (middle (m) stage), between 30 and 34 weeks (late (1) stage), and after 36 weeks of gestation. In addition to these periods, the postpartum period was examined on the 3rd day after delivery. In each period, 30 examinations were performed. The mean value was calculated in each period and hemodynamic changes in both limbs were assessed during and after pregnancy. Significant difference was defined as p<0.05.
Result : In the early stage, the diameters of the two veins had not yet changed, but the diameters gradually increased after 20 weeks of gestation. These changes in both veins were significant compared with those in non pregnant women (FV; non-preg. vs. m-stage, 1-stage; p<0.001, PV; non-preg. vs. m-stage, 1-stage; p<0.001. In comparison between the right and left side, diameters of both vessels on the left side were significantly increased only during the late stage of pregnancy (FV; It vs. rt, p<0.01 PV : lt vs. rt, p<0.001. In the assessment of blood flow, flow-velocity in both vessels was significant slower after 20 weeks of gestation compared with that in the non-pregnant state, but there was no significant differences on comparison between the right and the left vessels throughout pregnancy. After delivery, diameter and flow velocity immediately returned to that in the non-pregnant state. There were no patients with DVT in the present study.
Conclusion : It was confirmed that the left limb showed a higher risk of DVT than the right limb according to changes in the diameters of FV and PV during pregnancy. Pregnancy induced slow venous velocity but there were no significant changes between the right and left limbs in normal pregnancy. Therefore, it is likely that not only the diameters of the vessels but also measurement of flow-velocity with ultrasound equipment is important to detect pregnant women with a higher risk of DVT.
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