Evaluation of Low-Dose Aspirin to Prevent Preeclampsia in Pregnant People with Chronic Hypertension

Objective Our objective was to evaluate if the use of low-dose aspirin (LDA) among pregnant individuals with chronic hypertension (CHTN) reduces the rate of superimposed preeclampsia or other adverse maternal and neonatal outcomes.Study Design Our study included single-center cohort of pregnant individuals with CHTN who had a live birth after 23 weeks' gestation, between 2013 and 2018. The primary exposure was the use of LDA in pregnancy and the primary outcome was superimposed preeclampsia. LDA use was also evaluated by the timing of initiation, before or after 16 weeks' gestation. Secondary outcomes included preeclampsia subtypes (e.g., preeclampsia with severe features, early-onset disease), as well as adverse maternal and neonatal outcomes. Differences were analyzed by chi (2) , Fisher's exact, or t tests, with logistic regression to adjust for confounders.Results Of 11,825 deliveries during the study period, 494 (4.2%) occurred in women with CHTN. Among those with CHTN, 174 (35%) were prescribed LDA, most often 81 mg daily (173 out of 174, 99%). Baseline characteristics were similar between groups, but the history of preeclampsia was more common in those prescribed LDA. The rate of superimposed preeclampsia was no different among those with CHTN-prescribed LDA compared with those who were not (36% vs. 30%, p = 0.2), even when restricting the analysis to those prescribed LDA before 16 weeks' gestation (33 vs. 30%, p = 0.2). In addition, LDA did not lead to a reduction in the rate of preeclampsia with severe features, early-onset preeclampsia, or other adverse maternal outcomes. However, the composite rate of adverse neonatal outcomes was lower in LDA users versus nonusers (4.0 vs. 13%, p = 0.002), which persisted after multivariable adjustment (adjusted odds ratio: 0.28, 95% confidence interval: 0.12-0.67).Conclusion Among pregnant individuals with CHTN, LDA did not decrease the rate of superimposed preeclampsia. Further studies are warranted to validate our observed reduction in adverse neonatal outcomes and to determine if aspirin is more beneficial at dosages greater than 81 mg daily.