#349 An ASA a day when a baby's on the way?

#349 An ASA a day when a baby’s on the way?

CLINICAL QUESTION

QUESTION CLINIQUE

Is acetylsalicylic acid (ASA) effective in preventing complications in pregnant women at risk of preeclampsia?

BOTTOM LINE

RÉSULTAT FINAL

In women at risk for preeclampsia at ~12-28 weeks gestation, low-dose ASA (50-150mg) reduces risk of preeclampsia by an absolute ~2%, perinatal death by ~0.5%, and preterm birth by ~2% compared to placebo. The risk of postpartum hemorrhage is increased by up to ~1%.

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EVIDENCE

DONNÉES PROBANTES

7 systematic reviews (17-77 randomized controlled trials [RCTs]; 26,952-46,568 patients) from the last 5 years comparing ASA to placebo in pregnant women at varying preeclampsia risk.^1-7 ASA usually initiated ~12-28 weeks, continued until delivery. Results statistically significant unless indicated.
- Maternal Outcomes:
  - Preeclampsia: 5 systematic reviews (16-60 RCTs):^1-5
    - 5-9.6% versus 5.8-11.8% (placebo), number needed to treat (NNT)=31-72.
  - Placental abruption: 3 systematic reviews (9-29 RCTs):^1,3,4
    - 0.9-1.3% versus 0.7-1.2% (placebo) (not statistically different).
  - Postpartum hemorrhage (>500-1000mL blood loss): 4 systematic reviews (9-19 RCTs):^1,3,4,6
    - 7-15.2% versus 3.3-14.3% (placebo), number needed to harm (NNH)=97-239 (1/4 systematic reviews not statistically different).⁴
- Fetal outcomes:
  - Perinatal death: 3 systematic reviews (11-52 RCTs):^1,3,4
    - 1-3.1% versus 2.7-3.5% (placebo), NNT=179-239.
  - Preterm delivery/birth: 2 systematic reviews with comprehensive data (18-47 RCTs):^1,3
    - 0.9-16.6% versus 17.5-18.5% (placebo), NNT=54-64.
  - Fetal intracranial bleed: 1 systematic review (6 RCTs):⁴
    - Not statistically different.
- Limitations: Inconsistent definitions of patients at risk for preeclampsia; infrequent reporting of serious maternal outcomes (examples: eclampsia, death); some large RCTs not included in all systematic reviews.

CONTEXT
CONTEXTE

No clear difference in outcomes between 50-150 mg daily.^1,3-5,7
Earlier initiation (<16-20 weeks) may enhance preeclampsia benefit based on subgroup analyses. No consistent trends for other outcomes.^1-4,7
Sensitivity of clinical risk factors for predicting pre-eclampsia is <40%.⁸
Guidelines vary:
- Common recommendations among guidelines for ASA use include, but not limited to:
  - Any high-risk factors (examples: prior preeclampsia, chronic hypertension, renal or autoimmune disease, diabetes) or,
  - At least 2 moderate-risk factors (examples: nulliparity, age >35-40, previous adverse pregnancy outcome).
- Canadian: ASA 81-162mg daily preferably before 16 weeks until 36 weeks gestation.⁸
- American: ASA 81mg daily initiated between 12-28 weeks gestation (optimally before 16 weeks) until delivery.⁹