# Aspirin Prophylaxis for Pre-eclampsia

> Risk stratification, low-dose aspirin dose, timing of initiation and discontinuation for pre-eclampsia prevention in NEET-PG Obstetrics and Gynaecology.

- Canonical URL: https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/aspirin-prophylaxis-for-pre-eclampsia
- Exam / course: NEET-PG · Subject: Obstetrics and Gynaecology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-08
- Last updated: 2026-10-08
- Reference basis: USPSTF Recommendation on Aspirin Use to Prevent Preeclampsia; ACOG Practice Bulletin on Low-Dose Aspirin Use During Pregnancy; Williams Obstetrics
- How to cite: "Aspirin Prophylaxis for Pre-eclampsia", PrepElephant, https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/aspirin-prophylaxis-for-pre-eclampsia

## Direct answer

Low-dose aspirin prophylaxis is given to high-risk pregnant women to reduce preterm pre-eclampsia, usually 75 to 81 mg once daily. It is started between 12 and 28 weeks, ideally before 16 weeks, after a documented risk assessment at booking. Women with one high-risk factor, or two or more moderate-risk factors, qualify, and treatment continues until delivery in most protocols. Aspirin prevents pre-eclampsia but does not treat it once established.

## What you must remember

- **High-risk factors:** previous pre-eclampsia, multifetal pregnancy, chronic hypertension, pregestational diabetes, chronic kidney disease, and autoimmune disease such as systemic lupus erythematosus or antiphospholipid syndrome.
- **Moderate-risk factors:** nulliparity, obesity with BMI above 30, family history of pre-eclampsia, age 35 or above, low income, and an interpregnancy interval above 10 years.
- **Dose:** 75 to 81 mg once daily; higher analgesic doses are not used for prophylaxis.
- **Timing:** start between 12 and 28 weeks, ideally before 16 weeks.
- **Duration:** continue until delivery in most protocols, with stopping decisions left to the treating team.
- **Mechanism:** irreversible inhibition of platelet cyclo-oxygenase, reducing thromboxane A2 and improving placental vascular function.

## A risk-based pathway from booking to delivery

Aspirin is a preventive decision made early and reviewed throughout pregnancy. The steps below show the sequence that examiners expect.

1. **Screen at booking:** take a structured history for high-risk and moderate-risk factors and record each one.
2. **Classify risk:** one high-risk factor, or two or more moderate-risk factors, is the threshold for starting aspirin.
3. **Start in the window:** begin between 12 and 28 weeks, preferably before 16 weeks, since the earlier start is preferred.
4. **Dose and adherence:** prescribe 75 to 81 mg daily and check adherence at each antenatal visit.
5. **Continue to delivery:** keep aspirin going unless the team stops it for a specific reason, such as bleeding or planned surgery.
6. **Keep monitoring:** aspirin does not replace blood pressure checks, urine protein testing or the management of established hypertension.

Aspirin's benefit is confined to a defined group, so indiscriminate prescription adds bleeding risk without gain. The risk score at booking is the single most important record in this pathway.

## Where the exam tries to catch you

Questions in this area test the window, the indication and the difference between prevention and treatment.

- **Trap:** Starting aspirin after 28 weeks as a preventive measure. **Correct:** The window closes at 28 weeks, and the earlier start before 16 weeks is preferred.
- **Trap:** Using aspirin to treat established pre-eclampsia. **Correct:** Aspirin is prophylactic; established disease is managed with blood pressure control, magnesium sulphate and delivery as indicated.
- **Trap:** Prescribing aspirin to every pregnant woman. **Correct:** Prophylaxis is reserved for women who meet the risk criteria documented at booking.

## Frequently asked questions

### What dose of aspirin is used for pre-eclampsia prophylaxis?

Low-dose aspirin of 75 to 81 mg once daily is the usual dose for pre-eclampsia prophylaxis. Some guidelines allow other doses within a specified range. Aspirin for pre-eclampsia prophylaxis is always given at low dose, not at analgesic doses.

### When should aspirin be started for pre-eclampsia prophylaxis?

Aspirin for pre-eclampsia prophylaxis is started between 12 and 28 weeks of gestation, ideally before 16 weeks. The earlier start is preferred, and the usual window closes at 28 weeks. Starting after that point falls outside the standard indication.

### Which women qualify for aspirin prophylaxis?

Women with one high-risk factor, such as previous pre-eclampsia or chronic hypertension, qualify. Women with two or more moderate-risk factors, such as nulliparity or obesity, also qualify. Risk should be documented at booking and reviewed as pregnancy progresses.

### Is aspirin continued after delivery?

Aspirin prophylaxis is usually continued until delivery, and it is not needed after birth for pre-eclampsia. Decisions about stopping earlier, such as before planned surgery, rest with the treating obstetrician. Aspirin prophylaxis is a pregnancy-only indication.