Preeclampsia is a pregnancy-related condition that typically develops after 20 weeks. This condition, which affects both mother and baby, is caused by changes in blood pressure and the way the placenta functions. It may lead to symptoms like protein in the urine or complications involving the liver, brain, or blood.

During your pregnancy, a preeclampsia risk assessment may be offered around the time of your 13-week anatomy scan. This screening helps identify women who may benefit from early treatment or closer monitoring.

You might have questions about what it means to be in the “high-risk” category, how accurate the screening is, and whether being high risk means you will definitely develop preeclampsia.

In this fact sheet, we’ll cover the following:

1. What is Preeclampsia?
2. Who is considered high risk?
3. Screening and early detection
4. Preventative measures
5. Monitoring and management
6. Conclusion
7. Video transcript

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1. What is Preeclampsia?

Preeclampsia is a blood pressure syndrome that can affect some women from 20 weeks gestation onwards. It’s a condition unique to pregnancy that involves high blood pressure and signs of stress on other organs such as the kidneys, liver, and brain. One of the earliest indicators can be protein leaking into the urine.

In more serious cases, preeclampsia can lead to complications such as poor growth in the baby, or early delivery. Although these outcomes are rare, they highlight the importance of early detection and careful monitoring.

Preeclampsia is not the same as chronic high blood pressure, although the two can overlap. It develops specifically in pregnancy and usually resolves after birth, but it requires active management to reduce risks for both mother and baby.

2. Who is considered high risk?

A preeclampsia risk assessment helps identify women who may benefit from early intervention. This screening is usually performed during your 13-week ultrasound scan and combines information from your medical history, blood pressure, and specialised tests. It can detect up to 80% of women who may go on to develop early preeclampsia.

The threshold for being classified as “at risk” is low. If your estimated risk is 1% or greater, you will be considered in the high-risk group. This simply means your risk is higher than the background population, not that you will definitely develop the condition.

Factors that increase the chance of being classified as high risk include:

• A history of high blood pressure, kidney disease, diabetes, or autoimmune conditions
• First pregnancy or a large gap since your last pregnancy
• Multiple pregnancy (e.g. twins or triplets)
• Assisted conception (e.g. IVF)
• Family history of preeclampsia (mother or sisters)
• Higher maternal age or elevated BMI

Being labelled high risk can feel concerning, but it allows for preventative strategies and closer follow-up that can improve outcomes.

3. Screening and early detection

Preeclampsia risk screening is usually done at the time of your 13-week anatomy scan. It combines several pieces of information to estimate your individual risk. This includes:

• Your medical and pregnancy history
• Blood pressure readings
• Blood test results (including markers like PAPP-A and PlGF)
• Uterine artery Doppler measurements, which assess blood flow to the placenta

This assessment is designed to catch early signs of concern, well before any symptoms appear. If your risk is calculated at 1% or more, your care team may recommend starting preventative treatment.

It’s important to remember that the risk estimate is not a diagnosis. Many women identified as high risk go on to have healthy pregnancies without developing preeclampsia. The aim of early detection is to personalise care and reduce the likelihood of complications through early intervention.

4. Preventative measures

If you are identified as high risk for preeclampsia, your doctor may recommend starting preventative treatment early in pregnancy. One of the most effective measures is low-dose aspirin.

Research shows that taking 150 mg of aspirin each night from before 16 weeks gestation can reduce the risk or delay the onset of preeclampsia by up to 80%. This dose is equal to half of a standard 300 mg tablet and is usually taken at night. Most women will be advised to continue taking it until between 34 and 36 weeks of pregnancy.

This dose of aspirin is considered safe in pregnancy unless you have a known allergy or a medical reason not to take it. Always check with your doctor before starting.

5. Monitoring and management

If you are considered high risk for preeclampsia, your pregnancy care will usually include closer monitoring to detect any early changes. This may involve:

• Frequent blood pressure checks
• Urine testing for protein
• Regular blood tests to monitor kidney and liver function
• Ongoing growth scans to assess your baby’s development and placental function

Your care team will look for early signs that the condition may be developing so that timely decisions can be made. If preeclampsia is confirmed, medication may be prescribed to help control blood pressure.

In some cases, hospitalisation is needed, particularly if the condition worsens or your baby is not growing well. The goal is to continue the pregnancy safely for as long as possible, while reducing the risk of complications.

Monitoring helps your care team balance the needs of both mother and baby, aiming to optimise outcomes while planning the safest timing and mode of delivery.

6. Conclusion

Being identified as high risk for preeclampsia can be unsettling, but it provides an opportunity for early intervention and tailored care. With screening available from 13 weeks of gestation, many women at increased risk can benefit from proven preventative measures like low-dose aspirin.

Regular monitoring, growth scans, and blood pressure checks will help your care team manage your pregnancy safely. Most women in the high-risk category go on to have healthy pregnancies and births.

If you have questions about your risk, screening results, or treatment options, speak with your doctor. 

7. Video transcript

This is some information about your preeclampsia risk assessment and what it means if you are high risk. Preeclampsia is a blood pressure syndrome of pregnancy that can affect some women from 20 weeks gestation onwards. It causes high blood pressure, leaking protein in the urine and changes in the blood, brain and liver. In some rare cases. This can result in baby being small or born prematurely. Preeclampsia risk assessment identifies up to 80% of women who may develop this condition early. This risk assessment is performed at the time of your 13 week anatomy scan. It’s important to understand that we have a very low threshold for identifying someone at increased risk. If your risk is 1% or higher, you will fall into the at risk group. At risk means higher than the background population, but it certainly does not mean you will definitely develop the condition. It has been shown that starting aspirin before 16 weeks of pregnancy can reduce the chance or delay the onset of developing preeclampsia by up to 80%. The dose of aspirin recommended is 150 milligrams. This is half of a 300 milligram tablet. It’s best taken at nighttime every night until you are between 34 and 36 weeks gestation. This dose is considered safe, providing of course that you have no allergies or medical issues that prevent you from taking aspirin. Please check with your doctor to confirm that they are happy for you to commence aspirin. If you have any vaginal bleeding after commencing the aspirin, we recommend you cease its use and speak to your doctor for further advice.

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