Study Question: Does aspirin prevent preeclampsia and associated complications in high-risk women?

Setting: Various (meta-analysis)

Study Design: Meta-analysis (randomized controlled trials)

Synopsis: For this meta-analysis, the authors sought high-quality, randomized controlled trials of low-dose (by any definition) aspirin versus placebo for the prevention of pre-eclampsia and associated outcomes in women at high risk of preeclampsia based on history. Risk factors were previous preeclampsia, chronic (preexisting) hypertension, diabetes, renal disease, and advanced age at conception. Fourteen studies involving 12,416 women met the inclusion criteria. Analysis for publication bias was somewhat limited because of the small number of included studies but indicated that bias was unlikely. The results were generally reported as weighted odds ratios (ORs).

Results favored aspirin therapy for the diagnosis of preeclampsia (OR: 0.86; 95 percent confidence interval [CI], 0.76 to 0.96), prevention of perinatal death (OR: 0.79; 95 percent CI, 0.64 to 0.96), and prevention of preterm birth (OR: 0.86; 95 percent CI, 0.79 to 0.94). Results did not differ for bleeding complications (OR: 0.98; 95 percent CI, 0.79 to 1.21). Average birth weight was 215 g [7 lb, 8 oz] heavier in the aspirin-treated patients (95 percent CI, 90 to 340 g [3 lb to 11 lb, 14 oz]). Unfortunately, the methodology used did not include reporting of absolute risk differences, so we cannot calculate number needed to treat (NNT). It also is unclear whether specific historical factors are associated with more or less benefit from aspirin therapy.

Bottom Line: The literature published to date consistently shows that low-dose aspirin has a protective effect in women with risk factors for preeclampsia. It does not increase the risk of bleeding complications, including placental abruption. The methodology used did not permit determination of absolute risk reduction and NNT. (Level of Evidence: 1a)