Annals of hematology

Microparticle source and tissue factor expression in pregnancy.

PMID 25823853


Microparticles (MPs) bearing tissue factor (TF) are potent activators of the coagulation system. To investigate whether MPs originating from platelets or trophoblast cells contribute to coagulation changes in pregnancy, we aimed to characterize whether pregnancy, labor, and delivery are associated with changes in the origin and composition of circulating maternal MPs. We performed a prospective cohort study. Blood samples were collected in 20 non-pregnant women, 20 term pregnant women not in labor, and 20 term pregnant women in labor. Two samples were collected in the pregnant groups, the first prior to delivery and the second 1xa0h after delivery. MPs from platelets and trophoblasts and MPs expressing TF were identified using flow cytometry. Comparisons were made among the non-pregnant and pregnant groups, non-laboring and laboring groups, and predelivery and postdelivery values within the pregnant groups. Pregnancy was not associated with changes in MP origin or number of TF-expressing MPs. Neither labor nor delivery was associated with changes in the percentage of trophoblast-derived MPs in the pregnant groups. The percentage of platelet-derived MPs among laboring women increased after delivery (8.5 vs. 20.5xa0%, p = 0.02), although there was no difference with delivery in the non-laboring group. TF expression was not associated with delivery in either laboring or non-laboring women. In conclusion, pregnancy was not associated with changes in cell origin of circulating maternal MPs or in the number of TF-expressing MPs. However, labor and delivery appear to be associated with an increase in the number of platelet-derived MPs.