Is testing for aspirin response worthwhile in high-risk pregnancy?

OBJECTIVE: To explore the clinical impact of aspirin dosage adjustment in pregnant women at high risk of hypertensive disorders.

STUDY DESIGN: In this retrospective observational study including women with pre-existing hypertension, pre-gestational diabetes or previous placental-mediated complications, we compared the rates of pre-eclampsia, early-onset and severe pre-eclampsia between women who used 81 mg of aspirin (ASA) throughout pregnancy without platelet function analyser (PFA-100®) monitoring ("group ASA no PFA") and those in whom the aspirin dosage was adjusted according to PFA-100® results ("group ASA and PFA").

RESULTS: 270 women were included in the analyses, 111 in group ASA and PFA and 159 in group ASA no PFA. Aspirin was started before 13 weeks in 71.7% of women in group ASA no PFA and in 79.3% of those in group ASA and PFA. PFA-100® monitoring was associated with a lower rate of pre-eclampsia (15.3% vs. 30.8%; aOR 0.36, 95%CI 0.19-0.67) and severe pre-eclampsia (3.6% vs. 15.1%; aOR 0.22, 95% CI 0.07-0.66), after adjustment for various risk factors for pre-eclampsia. The rate of early-onset pre-eclampsia was not statistically different between the two groups (7.2% vs. 13.2%; aOR 0.42, 95%CI 0.17-1.04). The rate of pre-eclampsia was higher in women who needed an increase in aspirin dosage (11/43, 25.6%) than in those who did not (6/68, 8.8%, p=0.03).

CONCLUSION: Our results suggest that a strategy involving platelet function testing and individualized dosing is effective in preventing pre-eclampsia in high risk women. PFA testing should not be considered as standard practice, however, until prospective controlled randomized trials have confirmed these observations.