Platelet aggregation in citrated whole blood of the first trimester of pregnancy.

Background: It was recently suggested that platelet reactivity is reduced in early pregnancy. This study was performed to determine whether the citrated whole blood from 33 pregnant women in their first trimester showed spontaneous platelet aggregation and whether it differed in extent from that of 11 non-pregnant women.
Methods: The platelet count and number of platelet aggregates (PA) were serially determined in the same citrated whole blood specimens at 15, 30, 45, 60, 75, and 90min after blood sampling using a hematology analyzer.
Results: The number of PA increased significantly at 30min and thereafter in both groups, but was consistently lower for pregnant than non-pregnant women over the 90-min observation period. The platelet count decreased significantly in a time-dependent manner in both groups, but was significantly lower at 30 and 90min for non-pregnant than pregnant women. The number of PA showed a significant positive correlation with net decrease in platelet count for both pregnant and non-pregnant women. PA counts were also significantly positively correlated with the mean platelet volume.
Conclusion: Platelet reactivity monitored by the increase in number of PA and the fall in platelet count was reduced in early pregnancy compared with non-pregnant healthy controls.
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