#349 An ASA a day when a baby’s on the way?
CLINICAL QUESTION
Is acetylsalicylic acid (ASA) effective in preventing complications in pregnant women at risk of preeclampsia?
BOTTOM LINE
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
- 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
- 4.5-9.6% 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
- 3.7-15.2% versus 3.3-14.3% (placebo), number needed to harm (NNH)=97-239 (1/4 systematic reviews not statistically different).4
- Preeclampsia: 5 systematic reviews (16-60 RCTs):1-5
- Fetal outcomes:
- Perinatal death: 3 systematic reviews (11-52 RCTs):1,3,4
- 2.1-3.1% versus 2.7-3.5% (placebo), NNT=179-239.
- Preterm delivery/birth: 2 systematic reviews with comprehensive data (18-47 RCTs):1,3
- 15.9-16.6% versus 17.5-18.5% (placebo), NNT=54-64.
- Fetal intracranial bleed: 1 systematic review (6 RCTs):4
- Not statistically different.
- Perinatal death: 3 systematic reviews (11-52 RCTs):1,3,4
- 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.
- Maternal Outcomes:
CONTEXT
- 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
- Common recommendations among guidelines for ASA use include, but not limited to:
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Helpful knowledge
Great clarification
Interesting
Timely
very helpful
Gave me insight into the variety of doses we have been hearing about as well as duration. Have been initiating ASA ,when risk factors, btw 13 and 16 wks. We have listed obesity as a risk factor.
NNT high
This is good info and I will surely remember this when I see potential patients.
this is new to me
Useful information
good learning point
Other moderate risk factors to consider:
Family history of preeclampsia
(Mother or sister with history of preeclampsia)
In vitro conception (IVF)
(Conception via assisted reproductive technology)
Sociodemographic factors: Black race/ethnicity
{Increased risk due to systemic inequities, racism, and social determinants of health (not biological factors); aspirin may be considered with just one moderate factor in this case.}
Sociodemographic factors: Lower income
{Increased risk due to socioeconomic disparities and limited healthcare access; aspirin may be considered with just one moderate factor in this case.}
Personal history of low birth weight or small for gestational age (SGA) infant
{Prior infant with birth weight 10 years
More than 10 years since last pregnancy.