Low dose Aspirin and high-risk pregnancy: Evaluation of the effect of acetylsalicylic acid on the inhibition of platelet aggregation

Objective:

In obstetrics Aspirin® (acetylsalicylic acid) is used to prevent (recurrent) preeclampsia (PE) and other placental mediated adverse pregnancy outcomes in women with a positive screening for PE in the first trimester and in women in a following pregnancy after PE. International guidelines recommend the prescription of Aspirin® in a low dose (50 – 100 mg daily) at least from the 16th week until the 34th week of gestation to provide an optimal prophylactic effect. However, according to several studies risk reduction is achieved in 10 – 50%. A recent review postulates that a significant proportion of these patients exhibit suboptimal response to low-dose Aspirin® (LDA), which is biochemically measured as a diminished suppression of platelet activation. This phenomenon is clinically called 'aspirin-resistance', 'aspirin non-responsiveness' or 'aspirin- treatment failure'.

Method:

We conducted a retrospective study in high-risk obstetric women who take LDA-prophylaxis in order to prevent PE either because of a positive screening result on PE or because PE was diagnosed in a previous pregnancy. Aspirin® was prescribed in a dose of 100 mg daily and all patients started the prophylaxis before the 16th week gestational age. The aim of the study was to evaluate the effect of LDA on the inhibition of platelet activation. We used the light transmission aggregometry (LTA) to measure the platelet response to LDA. This method is based on the detection of light that passes through platelet-rich plasma containing aggregated platelets. It is the most used in vitro test of platelet function currently available and it is the gold standard to detect platelet disorders.

Results:

Data will be shown in the presentation.

Conclusion:

Clinical studies in cardiology, where antiplatelet agents are used for the prevention of coronary artery disease and cerebrovascular disease, show that equal doses of Aspirin® do not inhibit thrombocyte aggregation to the same extent in each patient. Consequently Aspirin® is administered in an individual dosage for each patient after evaluation of platelet function by biochemical assays. Based on this observation, we hypothesize that the respond to Aspirin® might vary substantially even in our study population, caused by the dose-dependent effect of LDA on the inhibition of platelet activation as mentioned above. We conclude that the current recommendation of 50 – 100 mg Aspirin® daily in the prevention of PE might not always block thrombocyte aggregation sufficiently, which might explain the data about the pregnancy outcomes after LDA- prophylaxis. This study provides new insights in the current understanding of the dose-dependent effect of LDA on the inhibition of platelet aggregation. It needs further investigation, because actually there is almost no research about this issue. In terms of personalized medicine we aim to improve the preventive effect of LDA by establishing an individualized management for high-risk obstetric patients to prevent adverse pregnancy outcomes more effectively.

No conflict of interest has been declared by the author(s).