Oral Concurrent Session 8 – Hypertension

Objective: Platelet activity may not be adequately inhibited by low dose aspirin (ASA) in some people at risk for hypertensive disorders of pregnancy (HDP), limiting the potential benefits of ASA prophylaxis.We investigated platelet activity in pregnancy and its association with ASA responsiveness.Study Design: Pregnancy Outcomes and Platelet PhenotYpes (POPPY) was a prospective cohort recruited in the first trimester and classified as high or low risk for HDP based on US Preventative Task Force Criteria.The high-risk group was recommended ASA 81mg daily (ASA group) and the low-risk group was not (controls).We evaluated serum thromboxane B2 (TxB2) and platelet indices at 11-14 weeks (pre-ASA) and 24-28 weeks (on ASA).Platelet aggregation was evaluated with arachidonic acid (AA) +/in vitro ASA, submaximal agonists (adenosine diphosphate [ADP], collagen, epinephrine [EPI]), and spontaneous platelet aggregation (SPA).ASA non-response was defined as >20% platelet aggregation with high-dose AA at 24-28 weeks.Results: Among 66 participants, 56 completed both blood draws (41 ASA compliant and 15 controls; Table).Among controls, platelet count and size did not change, whereas platelet immaturity and platelet aggregation increased with submaximal agonist stimulation.In the ASA group, ASA induced a 99% decrease in serum TxB2 (26.3 to 0.3 ng/ml, p < 0.001) and 70% decrease in platelet aggregation with AA (89% to 15%, p < 0.001).Submaximal agonists elicited a heterogeneous response; with 29%, 53%, and 31% decrease in platelet aggregation with ADP, collagen, and EPI, respectively (p < 0.05 for each).Despite near complete TxB2 inhibition, 31% of high-risk participants were ASA nonresponders.ASA non-responders had significantly higher levels of SPA and platelet aggregation with submaximal agonists at baseline (Figure ).Conclusion: Platelet immaturity and aggregation increase during pregnancy.While ASA reduced platelet aggregation, nearly 1 in 3 were ASA non-responsive, suggestive of inadequate platelet inhibition.First trimester platelet activity may identify nonresponders with potential clinical implications.