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Preeclampsia Risk & Low-Dose Aspirin Calculator (USPSTF / ACOG)

Check the USPSTF and ACOG risk factors for preeclampsia — high-risk and moderate-risk — to see whether low-dose aspirin (81 mg from 12–28 weeks) is recommended in your pregnancy.

Preeclampsia in a previous pregnancy

Twins or more (multifetal pregnancy)

Chronic high blood pressure

Type 1 or type 2 diabetes before pregnancy

Kidney disease

Autoimmune disease (lupus, antiphospholipid syndrome)

First pregnancy carried past 20 weeks (nulliparity)

BMI over 30

Mother or sister had preeclampsia

Age 35 or older

Pregnancy through IVF

Black race or low income (social and structural risk, per USPSTF)

Previous low-birth-weight baby, adverse outcome, or more than 10 years since last pregnancy

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How it works

recommend low-dose aspirin if (high-risk factors ≥ 1) or (moderate-risk factors ≥ 2) · high: prior preeclampsia, multifetal gestation, chronic hypertension, pregestational diabetes, kidney disease, autoimmune disease · moderate: nulliparity, BMI > 30, family history, age ≥ 35, IVF, Black race or low income, personal history factors · dose 81 mg/day from 12–28 weeks (best before 16) until delivery

Preeclampsia is high blood pressure with organ involvement after 20 weeks of pregnancy. Taking low-dose aspirin daily from early pregnancy lowers the risk by about 15% (and preterm birth by 14%) in people at increased risk. The US Preventive Services Task Force and ACOG recommend it for anyone with at least one high-risk factor or more than one moderate-risk factor. Many guidelines outside the US (NICE, FIGO, Spain, Latin America) use 75–150 mg taken at night, so follow the dose your clinician prescribes.

Worked example

A first pregnancy (nulliparity) with a BMI over 30 and no high-risk factors: 0 high-risk and 2 moderate-risk factors. Two moderate factors meet the threshold, so the result is Low-dose aspirin recommended — 81 mg daily from 12–28 weeks, ideally before 16 weeks, until delivery.

Sources: USPSTF (2021): Aspirin use to prevent preeclampsia · ACOG Committee Opinion 743: Low-dose aspirin use during pregnancy

Frequently asked questions

Who should take baby aspirin to prevent preeclampsia?

Pregnant people with one high-risk factor (previous preeclampsia, twins or more, chronic hypertension, diabetes, kidney or autoimmune disease) or more than one moderate-risk factor (first pregnancy, BMI over 30, family history, age 35+, IVF, sociodemographic risk, previous adverse outcome).

When should I start aspirin for preeclampsia?

Between 12 and 28 weeks, ideally before 16 weeks, and continue daily until delivery. Starting later than 28 weeks has not shown benefit.

Is low-dose aspirin safe in pregnancy?

Large reviews show 60–150 mg a day does not increase miscarriage, birth defects, placental abruption or serious bleeding. Do not start it without talking to your clinician, especially with a bleeding disorder or aspirin allergy.

Why is the dose 81 mg in the US but 100–150 mg elsewhere?

US guidance is built on 81 mg tablets used in trials; the large ASPRE trial used 150 mg at night, which NICE, FIGO and many countries now prefer for high-risk pregnancies. Both are low doses; your clinician will choose.

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Educational information only, not medical advice or a diagnosis. Discuss your results and any decision with your doctor, midwife or pharmacist.