ACOG Preeclampsia Prophylaxis Risk Assessment: Adverse Pregnancy Outcomes
According to ACOG guidelines for preeclampsia prophylaxis risk assessment, "history of preeclampsia" is the primary adverse pregnancy outcome considered, particularly early-onset preeclampsia with preterm delivery at less than 34 0/7 weeks of gestation, or more than one prior pregnancy complicated by preeclampsia. 1
High-Risk Adverse Pregnancy Outcomes
The ACOG Committee Opinion No. 743 (2018) specifically identifies the following prior adverse pregnancy outcomes that qualify as high-risk factors warranting aspirin prophylaxis:
Primary Adverse Outcome
- History of preeclampsia - especially:
- Early-onset preeclampsia with preterm delivery <34 0/7 weeks
- More than one prior pregnancy complicated by preeclampsia 1
Associated Adverse Outcomes in Prior Pregnancies
While not explicitly listed as standalone criteria in the risk assessment framework, the evidence shows these adverse outcomes are strongly associated with preeclampsia history and recurrence risk:
- HELLP syndrome (hemolysis, elevated liver enzymes, low platelet count) 2
- Placental abruption 2
- Stillbirth 2
Important Clinical Context
The ACOG framework focuses on preeclampsia history as the adverse pregnancy outcome, rather than listing multiple separate adverse outcomes. This differs from how clinicians might conceptualize "adverse pregnancy outcomes" more broadly. The guideline specifically states that aspirin prophylaxis is recommended for women with one or more high-risk factors, with history of preeclampsia being the pregnancy-specific high-risk factor 1, 3.
Risk Stratification Details
Women with previous early-onset preeclampsia have a 4.22-fold increased risk of recurrent preeclampsia in subsequent pregnancies 2. The recurrence risk is particularly elevated when:
- Previous preeclampsia was early-onset (<34 weeks)
- HELLP syndrome complicated the prior pregnancy
- Placental abruption occurred
- Stillbirth resulted
Common Pitfall to Avoid
Do not confuse the moderate-risk factors with adverse pregnancy outcomes. The moderate-risk category includes factors like first pregnancy, maternal age ≥35 years, BMI >30, and family history of preeclampsia - these are risk factors, not prior adverse outcomes 1. Only history of preeclampsia itself qualifies as the adverse pregnancy outcome in the ACOG risk assessment framework.
Timing Considerations
When history of preeclampsia is present, aspirin prophylaxis (81 mg/day) should be initiated between 12-28 weeks of gestation, optimally before 16 weeks, and continued daily until delivery 1, 3.