(588) Use of low dose aspirin and timing of preeclampsia with severe features diagnosis and delivery

Low dose aspirin (LDASA) is used to mitigate odds of developing preeclampsia, and some data suggest that it also delays onset of diagnosis. Our objective was to evaluate the association between LDASA and timing of preeclampsia with severe features (PEC-SF) diagnosis and medically-indicated preterm delivery.


Study Design:

This retrospective cohort study included patients diagnosed with antepartum PEC-SF as defined by ACOG who delivered at two academic medical centers over two years. The exposure of interest was LDASA use during pregnancy. The primary outcome was gestational age < 37 weeks at time diagnosis of PEC-SF. The secondary outcomes were delivery at < 37 weeks and < 34 weeks, and < 34 weeks at time of PEC-SF diagnosis. Multivariable logistic regression models were used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for preterm birth. Kaplan-Meier curves were generated to examine timing of diagnosis and timing of delivery for those reporting LDASA and those not reporting LDASA.


Results:

Of 774 patients with PEC-SF, 186 (24%) reported LDASA and comprise the analysis cohort. Of the 186, 124 (67%) were diagnosed with preterm PEC-SF at < 37 weeks, and 58 (31%) at < 34 weeks. Compared to non-LDASA users, LDASA use was not associated with PEC-SF at < 37 weeks or < 34 weeks (Table 1). The Kaplan-Meier curves comparing the timing of PEC-SF diagnosis and timing of delivery between LDASA users and non-users demonstrate no meaningful difference between the two groups (Figure 1).


Conclusion:

In this diverse population, the modest, non-significant increase in odds of preterm diagnosis and delivery < 37 weeks among ASA users reflects confounding by indication, as patients prescribed LDASA have higher baseline risk of PEC-SF.