Low-dose aspirin for the prevention of superimposed preeclampsia in women with chronic hypertension: a systematic review and meta-analysis

OBJECTIVE: This systematic review and meta-analysis investigated whether the use of low-dose aspirin during pregnancy by women with chronic hypertension reduces the odds of superimposed preeclampsia and poor perinatal outcomes. DATA SOURCES: In September 2021, the following sources were searched: Embase, MEDLINE, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform, and EU Clinical Trials Register. Only human studies were included, with no time or language restrictions. STUDY ELIGIBILITY CRITERIA: Cohort, case-control, and randomized controlled studies reporting women with chronic hypertension pregnant with a singleton were included. Eligible studies compared low-dose aspirin use during pregnancy with a control arm. METHODS: Risk of bias was assessed using the RoB 2 and ROBINS-I tools. A meta-analysis was performed using a random-effects model, estimating odds ratios and 95% confidence and prediction intervals, and the quality of data was assessed with the GRADE approach. Heterogeneity was investigated in regard to study methodology, timing of commencement of aspirin, and the outcome of preterm preeclampsia. RESULTS: Nine studies (3 retrospective cohort studies and 6 randomized trials) including 2150 women with chronic hypertension were included. Low-dose aspirin prophylaxis did not significantly reduce the odds of superimposed preeclampsia in the randomized controlled trials (odds ratio, 0.83; 95% confidence interval, 0.55-1.25; prediction in-terval, 0.27-2.56; low-quality evidence) or observational studies (odds ratio, 1.21; 95% confidence interval, 0.78-1.87; prediction interval, 0.07-20.80; very low-quality evi-dence). Low-dose aspirin also did not reduce the odds of preterm preeclampsia (odds ratio, 1.17; 95% confidence interval, 0.74-1.86), and early aspirin initiation had no significant impact. There was no significant effect on small-for-gestational-age neonates or perinatal mortality; however, there was a significant reduction in preterm birth (odds ratio, 0.63; 95% confidence interval, 0.45-0.89; moderate-quality evidence). The quality of the evidence is limited by heterogeneity and risk of bias. CONCLUSION: This meta-analysis was unable to demonstrate a significant change in the odds of superimposed preeclampsia, small-for-gestational-age infants, or perinatal mortality with the use of low-dose aspirin in women with chronic hypertension. However, significant reduction in preterm birth justifies the continued use of aspirin prophylaxis. This work was prospectively registered on the International Prospective Register of Systematic Reviews (registration number CRD42021285921).