Hemorheological studies on platelet counts and size in normal pregnancy and pregnancies with preeclampsia and intrauterine growth retardation

: It has been reported that preeclampsia and pregnancy resulting in intrauterine growth retardation (IUGR) are associated with high hematocrits. The relations between hematocrits (Ht) and platelet volumes in normal and abnormal pregnancies were investigated to clarify a hemorheological effect on formation of microthrombus. 1) In normal pregnancy, Ht was decreased from 12-19 weeks gestation and reached its lowest level at 28-31 weeks gestation. The mean platelet volume (MPV) was decreased from 20 to 31 weeks gestation but markedly increased from 38 to 41 weeks gestation. The platelet count (Pl) remained unchanged during pregnancy. 2) In severe type of preeclampsia, at 28-37 weeks gestation Ht and MPV were markedly increased and Pl was markedly decreased at 38-41 weeks gestation as compared with normal pregnancies. 3) Mothers who delivered IUGR had a much higher level of Ht at 28-35 weeks gestation and MPV level from 38 weeks gestation than in normal mothers. As the volume of young platelets is large, increased MPV is suggestive of the occurrence of platelet consumption. From these results, it was suggested that microcirculatory disturbances such as higher blood viscosity due to hemoconcentration and microthrombus formation were related to the onset of preeclampsia or IUGR.