PB1275 - Platelet contractility before and during pregnancy in women with a bad obstetric history

Background: Platelets play a crucial role in the development of obstetric complications. Contractility is a platelet function with understudied (patho)physiological obstetric implications.

Aims: To study platelet contractility in women with a bad obstetric history (BOH) receiving early thromboprophylaxis in the preconception period and during pregnancy

Methods: The study was approved by the Ethical Committee of Kazan Federal University with written consent obtained. The main group included 115 women with BOH (miscarriages, premature births) and the control group included 33 parous women without past obstetric complications. Platelet functionality was assessed before and during pregnancy 3-11 times using an optical blood clot contraction assay correlated with expression of activation markers determined by flow cytometry before/after stimulation. All the patients with BOH received enoxaparin prophylactically since the preconception period and aspirin since the 1st trimester throughout the pregnancy

Results: Before the pregnancy, the median extent of clot contraction in women with BOH was decreased compared with the control (Figure 1). The impaired baseline clot contraction partially normalized in the first trimester and fully normalized in the second and third trimesters of pregnancy, becoming indistinguishable from the control (Figure 1). Platelet reactivity in response to TRAP assessed by expression of P-selectin and active αIIbβ3 followed the same trend: it was reduced initially and normalized during pregnancy (not shown). Individual time-dependent variations of the extent of clot contraction revealed that in 61% of the pregnant women with BOH, an increase (normalization) in the clot contraction occurred a few weeks after administration of aspirin (Figure 2)

Conclusion(s): In women with BOH, the initial platelet dysfunction was found to be associated with chronic background platelet activation. Platelet contractility and reactivity normalized gradually during the pregnancy, likely due to the early prescription of enoxaparin and aspirin, which alleviated platelet activation and secondary exhaustion and dysfunction