Preeclampsia Risk Assessment Calculator — ACOG Screening Guidelines
The Preeclampsia Risk Assessment tool screens pregnant patients for high-risk and moderate-risk factors to determine the need for low-dose aspirin prophylaxis, based on ACOG Practice Bulletin recommendations.
About
Preeclampsia is a hypertensive disorder of pregnancy affecting 2-8% of pregnancies worldwide and a leading cause of maternal and perinatal morbidity and mortality. The ACOG (American College of Obstetricians and Gynecologists) screening approach classifies patients into high-risk (any one of six factors: previous preeclampsia, multifetal gestation, chronic hypertension, pregestational diabetes, renal disease, or autoimmune disease) and moderate-risk categories (nulliparity, obesity BMI >30, family history of preeclampsia, maternal age ≥35, interpregnancy interval >10 years, or IVF pregnancy). Patients with any single high-risk factor or two or more moderate-risk factors are recommended low-dose aspirin (81 mg) prophylaxis starting between 12-16 weeks of gestation to reduce the risk of developing preeclampsia.
Formula
Risk = Any high-risk factor (1) OR ≥2 moderate-risk factors = High risk
The Preeclampsia Risk Assessment is not a numerical score but a categorical screening tool. The clinician checks for the presence of each risk factor. If the patient has any one of the six high-risk factors (previous preeclampsia, multifetal gestation, chronic hypertension, pregestational diabetes, renal disease, or autoimmune disease such as SLE or APS), they are classified as HIGH RISK and aspirin prophylaxis is recommended. If the patient has no high-risk factors, the moderate-risk factors are counted: nulliparity, BMI >30, family history of preeclampsia, age ≥35, interpregnancy interval >10 years, and IVF pregnancy. If two or more moderate-risk factors are present, the patient is also classified as HIGH RISK. If exactly one moderate-risk factor is present, the patient is classified as MODERATE RISK and aspirin may be considered. If no risk factors are present, the patient is LOW RISK. This approach follows the 2018 ACOG Practice Bulletin No. 202 and the USPSTF 2021 recommendation on aspirin prophylaxis for preeclampsia prevention.
Score Interpretation
Preeclampsia affects 2-8% of pregnancies and is a leading cause of maternal mortality worldwide, responsible for an estimated 50,000-70,000 maternal deaths annually. The ACOG screening approach, endorsed by USPSTF, identifies patients at increased risk who benefit from low-dose aspirin prophylaxis, which reduces the risk of preeclampsia by approximately 24%, preterm birth by 15%, and IUGR by 20%. Aspirin prophylaxis is most effective when started before 16 weeks of gestation. This screening tool is designed for the first prenatal visit to guide timely prophylaxis initiation.
Low Risk — Routine Prenatal Care — 0–0
No high-risk or moderate-risk factors present. Standard prenatal follow-up.
Management: No aspirin prophylaxis. Continue routine prenatal care with standard BP monitoring.
Moderate Risk — Consider Aspirin — 1–1
One moderate-risk factor present. Aspirin prophylaxis may be considered.
Management: Consider low-dose aspirin (81 mg/day) from 12 weeks. Monitor BP at each visit.
High Risk — Aspirin Recommended — 2–100
Any high-risk factor OR ≥2 moderate-risk factors. Strongly recommend aspirin prophylaxis.
Management: Low-dose aspirin (81 mg/day) 12-16 weeks. Calcium if low intake. Weekly BP. Serial growth US.
Reference Ranges
| Population | Normal Range | Notes |
|---|---|---|
| Pregnant women at first prenatal visit | Low Risk: 0 risk factors | Moderate: 1 moderate factor | High: ≥1 high OR ≥2 moderate factors | ACOG and USPSTF recommend screening at the first prenatal visit. |
Dr. Mahmoud El-Sayed
Dr. Mahmoud is an endocrinology consultant with expertise in metabolic and endocrine disorders during pregnancy.
View medical review board & editorial policy →Example Calculation
A 36-year-old primigravida (first pregnancy, nulliparous), BMI 32, with a family history of preeclampsia (her mother had severe preeclampsia). No high-risk factors. Moderate-risk factors: nulliparity (1), BMI >30 (1), maternal age ≥35 (1), family history of preeclampsia (1). Total moderate-risk factors: 4. Since ≥2 moderate-risk factors are present, she is classified as HIGH RISK. Recommendation: Low-dose aspirin (81 mg) daily starting between 12-16 weeks of gestation, calcium supplementation (1 g/day) if dietary intake is low, weekly BP monitoring, and serial growth ultrasounds.
Related Conditions
Related Medications
Common Mistakes
Counting gestational hypertension or preeclampsia in the current pregnancy as a risk factor
This screening is performed at the first prenatal visit to predict risk. Current gestational hypertension or preeclampsia is a diagnosis, not a risk factor for the same pregnancy.
Starting aspirin after 16 weeks of gestation
Aspirin prophylaxis should be initiated between 12-16 weeks for maximal benefit. Starting after 16 weeks significantly reduces efficacy in preventing preeclampsia.
Frequently Asked Questions
When should aspirin prophylaxis for preeclampsia be started?
What defines a high-risk factor for preeclampsia according to ACOG?
What is the role of calcium supplementation in preeclampsia prevention?
References
- ACOG Practice Bulletin No. 202: Gestational Hypertension and Preeclampsia. Obstet Gynecol. 2019;133(1):e1-e25. PubMed
- NICE Guideline NG133: Hypertension in pregnancy: diagnosis and management. National Institute for Health and Care Excellence, 2019 (updated 2023).
- USPSTF. Aspirin Use to Prevent Preeclampsia and Related Morbidity and Mortality. JAMA. 2021;326(12):1186-1191. PubMed