Summary
Platelet activation has a key role in mediating thrombotic and inflammatory events.
This study aimed to determine the influence of the menstrual cycle, pregnancy and
preeclampsia on in vivo platelet activation. Twelve healthy nulliparous, non-smoking women with regular menses
were studied over a single menstrual cycle. Twenty-one healthy primigravida pregnant
women were studied longitudinally at 16, 24, 32 and 37 weeks gestation and seven weeks
post-partum. Sixteen primigravida women with preeclampsia were studied at time of
diagnosis and at seven weeks post-partum. Platelet-monocyte aggregates and platelet-surface
P-selectin expression were assessed by flow-cytometry. Soluble P-selectin and CD40
ligand (CD40L) were measured by ELISA. Markers of platelet activation did not vary
over the menstrual cycle. Platelet-monocyte aggregates were greater in the third trimester
of pregnancy compared to non-pregnant women (p=0.003). Platelet surface and plasma
soluble P-selectin concentrations increased with gestation (p<0.0001) and were raised
by 24 weeks of pregnancy compared to non-pregnant women (p≤0.02 for both) and together
with platelet monocyte aggregates, decreased post-partum (p≤0.02). Soluble CD40L concentrations
fell in pregnancy, reaching a nadir at mid-gestation (p=0.002). There were no differences
in markers of platelet activation between normal and pre-eclamptic pregnancies. In
conclusion, platelet activation is increased in pregnancy and increases with gestation
but is unaffected by preeclampsia. This suggests that systemic platelet activation
is a feature of pregnancy but this is not affected by established preeclampsia.
Keywords
Platelet activation - platelet-monocyte aggregates - pregnancy - preeclampsia