Abstract
The influence of a change in red blood cell (RBC) concentration on the initiation time of blood coagulation (Ti) in pregnant and non-pregnant females was investigated using a damped oscillation rheometer to evaluate the risk of hemorrhagic tendency or thrombus formation. The blood samples from 40 female volunteers (20 pregnants and 20 non-pregnants) were examined. After centrifuging some portion of each blood sample, an appropriate volume was taken from the RBC layer to make an artificially diluted blood, or to add it to the autologous blood, making an artificially concentrated blood. The Ti of non-pregnant females was significantly reduced with increasing the RBC concentration from 3.75±0.25 to (5.75±0.25)×106/mm3. However, the Ti of pregnant females showed almost no change in the RBC concentrations from 3.25±0.25 to (5.25±0.25)×106/mm3. These results suggest that RBC concentration plays an important role in accelerating the initial coagulation reaction of blood of non-pregnant females and that a hypercoagulant condition caused by pregnancy conceals the effect that changes in RBC concentration have in pregnant females.