A large real-world study found that routine aspirin use was linked to less severe preeclampsia and later onset of severe disease in pregnant patients.
- Daily aspirin was associated with a 29% lower rate of severe preeclampsia
- Severe preeclampsia developed later among patients who still developed the condition
- Aspirin is not recommended for every pregnant woman and should only be taken under medical guidance
Preeclampsia (a pregnancy-related condition marked by high blood pressure and signs of organ damage) can turn a seemingly healthy pregnancy into a medical emergency. The condition is marked by high blood pressure (https://www.medindia.net/health/conditions/high-blood-pressure.htm) during pregnancy and may involve damage to organs such as the kidneys, liver, or brain.
When severe features develop, the risks to both mother and baby can become much greater.
New research suggests that starting daily aspirin early in pregnancy may help reduce this risk.
In a population with a high burden of preeclampsia, routine aspirin administration was associated with a 29% reduction in preeclampsia with severe features (SPE) compared with the period before the practice was introduced (1✔ ✔Trusted Source
LB02 | Universal Aspirin Administration for Prevention of Preeclampsia
Go to source)(2✔ ✔Trusted Source
New Study: Routine Aspirin Therapy Prevents Severe Preeclampsia in At-Risk Populations
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How Did Aspirin Affect Severe Preeclampsia?
Researchers began giving pregnant patients 162 mg of aspirin daily at their first prenatal visit if they were 16 weeks pregnant or earlier.
The aspirin was provided directly at the clinic so patients did not have to obtain it themselves. Researchers compared outcomes after this practice was introduced with outcomes from patients treated before the change.
| Study Finding | What It Means |
|---|---|
| 29% lower rate of severe preeclampsia | Daily aspirin was associated with a lower chance of developing the most serious form of the condition. |
| Severe preeclampsia developed later | Even when the condition occurred, its onset was delayed in patients who received aspirin. |
| Lower risk among women with chronic hypertension | Women who already had high blood pressure before pregnancy also appeared to benefit. |
| No increase in maternal bleeding or placental abruption | The researchers did not find these major complications occurring more often with the aspirin strategy. |
The study included 18,457 patients who delivered between 2023 and 2025 after the aspirin program began. The researchers said that providing aspirin directly through prenatal clinics may have helped overcome barriers to starting preventive treatment.
The lead researcher said the approach appeared to delay severe preeclampsia and potentially prevent it in some patients. However, the researchers cautioned that the findings may not apply in exactly the same way to every pregnant population.
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Why Can Severe Preeclampsia Be Dangerous?
Preeclampsia usually develops after 20 weeks of pregnancy and can affect both the mother and baby. Severe preeclampsia can cause:
- Very high blood pressure, which can become life-threatening.
- Kidney and liver damage and problems affecting the brain or other organs.
- Placental problems, which can affect the baby’s growth.
- Preterm birth (https://www.medindia.net/news/preterm-birth-warning-signs-and-safety-precautions-to-take-during-pregnancy-207321-1.htm), especially when early delivery is needed to protect the mother or baby.
A recent study published in Scientific Reports reports that preeclampsia affects about 2% to 8% of pregnancies worldwide, with a greater burden in low- and middle-income countries (3✔ ✔Trusted Source
Early initiation of low-dose aspirin for the prevention of pre-eclampsia in high-risk pregnancies
).
The condition is also an important cause of pregnancy-related deaths. Hypertensive disorders of pregnancy accounted for 7.7% of pregnancy-related deaths in the United States in 2024.
This is why early monitoring, identifying women at higher risk, and appropriate prevention are important during pregnancy.
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How Could Aspirin Help Prevent Preeclampsia?
Preeclampsia can involve problems with placental development, blood flow, and inflammation. Low-dose aspirin may help by improving some of these processes:
- Improves blood flow: Aspirin may help blood flow more easily through the placenta.
- Reduces blood clotting: It reduces platelet clumping, which may support better circulation.
- May lower inflammation: Aspirin can affect inflammatory processes that are linked to preeclampsia.
- May support placental function: By influencing blood flow and inflammation, aspirin may help reduce processes involved in the development of the condition.
A systematic review published in Cureus also describes reduced platelet aggregation and inflammation as possible ways aspirin may help prevent preeclampsia (4✔ ✔Trusted Source
Preventing Preeclampsia With Low-Dose Aspirin: A Systematic Review of Efficacy Across Diverse Populations
).
Problems linked to preeclampsia can begin during early placental development, before symptoms appear.
This may explain why starting low-dose aspirin early in pregnancy, when recommended for women at risk, can be more effective than waiting until blood pressure problems develop.
Can Starting Aspirin Early Lower Pregnancy Risks?
A randomized controlled trial looked at whether starting aspirin before 12 weeks of pregnancy could help women at high risk of preeclampsia. Participants received 75 mg of aspirin daily or a placebo until 36 weeks of pregnancy or delivery.
The results showed lower rates of several complications in the aspirin group:
| Pregnancy Outcome | Aspirin Group | Control Group | What Does This Mean? |
|---|---|---|---|
| Preeclampsia | 8.9% | 28.6% | About 9 in 100 women in the aspirin group developed preeclampsia, compared with about 29 in 100 without aspirin. |
| Fetal growth restriction | 4.4% | 19.0% | About 4 in 100 babies had restricted growth with aspirin, compared with 19 in 100 in the control group. |
| NICU admission | 8.9% | 28.6% | About 9 in 100 newborns needed NICU care with aspirin, compared with about 29 in 100 in the control group. |
| Composite neonatal morbidity | 8.9% | 31.0% | A combined measure of serious newborn complications occurred in about 9 in 100 babies with aspirin versus 31 in 100 in the control group. |
| Preterm birth | 2.2% | 9.5% | Preterm birth was less common with aspirin, but the difference was not statistically significant, so the study cannot confirm that aspirin caused this reduction. |
| Perinatal death | 0% | 2.4% | No deaths occurred in the aspirin group, compared with a small number in the control group, but the difference was not statistically significant. |
The clearest finding was the difference in preeclampsia: roughly 29 out of every 100 women in the control group developed the condition compared with about 9 out of every 100 who received aspirin.
Overall, the trial adds to evidence that starting aspirin early in pregnancy may be important for women at high risk of preeclampsia, but the decision to use aspirin and the appropriate dose should be made with a healthcare professional.
Who May Be at Higher Risk of Preeclampsia?
Aspirin is not something every pregnant person should start on their own. Doctors assess individual risk before recommending preventive aspirin.
Common high-risk factors include:
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| Risk factor | Why it matters |
|---|---|
| Previous preeclampsia | Strong predictor of recurrence |
| Chronic hypertension | Increases risk of pregnancy-related hypertensive complications |
| Type 1 or type 2 diabetes | Associated with increased preeclampsia risk |
| Kidney disease | Can increase maternal vascular risk |
| Autoimmune disease | Conditions such as lupus or antiphospholipid syndrome can increase risk |
| Multiple pregnancy | Twins or higher-order pregnancies carry greater risk |
| Obesity | Strongly associated with preeclampsia |
| First pregnancy | Recognized moderate-risk factor |
| Maternal age 35 years or older | Can contribute to risk |
| Family history of preeclampsia | May increase individual susceptibility |
What Should Pregnant Women Know About Starting Aspirin?
Before starting low-dose aspirin, pregnant women should discuss their risk factors, timing and appropriate dose with their healthcare provider. Important points include:
- Low-dose aspirin may be recommended for women at higher risk of preeclampsia, usually starting between 12 and 28 weeks, ideally before 16 weeks.
- Risk factors include previous preeclampsia, multiple pregnancy, kidney disease, autoimmune disease, diabetes, and chronic hypertension.
- Dose varies: the new study used 162 mg, while another trial used 75 mg. The dose should be decided by a healthcare professional.
- Aspirin may not be suitable for women with aspirin/NSAID allergies, aspirin-related asthma, stomach ulcers, or bleeding disorders.
- Do not start, change, or stop aspirin during pregnancy without medical advice.
- Aspirin can lower the risk of preeclampsia but does not guarantee that it will be prevented.
Overall, the new evidence supports the potential benefit of early, medically supervised aspirin use in women at increased risk. However, aspirin is not a one-size-fits-all treatment, and regular prenatal monitoring remains essential.
Frequently Asked Questions
Q: Can aspirin prevent preeclampsia?
A: Low-dose aspirin can reduce the risk of preeclampsia in some high-risk pregnancies, but it does not guarantee prevention.
Q: How much did aspirin reduce severe preeclampsia in the new study?
A: Daily aspirin was associated with a 29% lower rate of preeclampsia with severe features.
Q: When is aspirin usually started during pregnancy?
A: For patients who are advised to take it, aspirin is generally started relatively early in pregnancy, with some guidance recommending initiation before 16 weeks. The exact timing should be decided by the treating clinician.
Q: Should every pregnant woman take aspirin?
A: No. Aspirin is generally considered based on individual risk factors and should not be started without medical advice.
Q: Is aspirin safe during pregnancy?
A: Low-dose aspirin can be appropriate for certain pregnant patients under medical supervision. Higher doses are different and may carry risks during pregnancy.
Q: Who may be at higher risk of preeclampsia?
A: Risk can be higher with previous preeclampsia, chronic hypertension, diabetes, kidney disease, autoimmune disease, multiple pregnancy and several other factors.
Q: Does the 162 mg dose apply to everyone?
A: No. The 162 mg dose was used in the Parkland study, but different studies have evaluated different low-dose regimens. The appropriate dose should be decided by a healthcare professional.
References:
- LB02 | Universal Aspirin Administration for Prevention of Preeclampsia –
(https://obgyn.onlinelibrary.wiley.com/doi/10.1002/pmf2.70204) - New Study: Routine Aspirin Therapy Prevents Severe Preeclampsia in At-Risk Populations –
(https://www.smfm.org/news/new-studyroutine-aspirin-therapypreventsseverepreeclampsiainat-risk-populations) - Early initiation of low-dose aspirin for the prevention of pre-eclampsia in high-risk pregnancies –
(https://www.nature.com/articles/s41598-025-28078-3) - Preventing Preeclampsia With Low-Dose Aspirin: A Systematic Review of Efficacy Across Diverse Populations –
(https://pmc.ncbi.nlm.nih.gov/articles/PMC12167430/)
Source-Medindia