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Acetylsalicylic Acid for Preventing Preeclampsia in Pregnant Women

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is studying preeclampsia, a pregnancy condition that can cause high blood pressure and other problems for the mother and baby. The treatment being used is acetylsalicylic acid, also known as aspirin. The purpose of the study is to find out whether stopping aspirin between weeks 24 and 26 of pregnancy works as well as continuing it until week 36 for preventing preterm preeclampsia.

In the study, pregnant participants will take aspirin by mouth during pregnancy, and then one group will stop it earlier while the other group will continue it longer. The study will then compare the two approaches to see whether stopping aspirin earlier is still safe for the mother and baby and whether it may lower the risk of bleeding in the mother.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Start of the trial

    Your trial participation begins after you join the study. The trial is designed to compare two ways of using acetylsalicylic acid, which is also called asa or aspirin.

    The study focuses on preeclampsia, a pregnancy condition that can cause high blood pressure and other problems during pregnancy.

  2. Step 2

    Aspirin treatment during pregnancy

    You take acetylsalicylic acid by mouth at a dose of 150 mg once daily.

    One study group stops asa between week 24 and week 26 of pregnancy.

    The control group continues asa until week 36 of pregnancy.

  3. Step 3

    Trial comparison period

    The trial compares whether stopping asa at 24 to 26 weeks is no worse than continuing it until 36 weeks in preventing preterm preeclampsia, which means preeclampsia that happens before full term.

    The trial also checks whether stopping asa changes the risk of problems for the mother, the baby during pregnancy, or the newborn, and whether it lowers the risk of bleeding in the mother.

  4. Step 4

    End of the trial

    The study is planned to run until 2028-12-30.

    The trial does not describe any other treatment steps beyond the asa schedule and the comparison of outcomes during pregnancy and after birth.

Who can join the trial?

7 criteria

  • Be older than 18 years.
  • Be able to read and understand the informed consent, which is the written form that explains the study and must be signed before joining.
  • Have a singleton pregnancy, meaning one baby is being carried.
  • Have had first-trimester preeclampsia screening between 11 weeks 0 days and 13 weeks 6 days of pregnancy using a multiparametric algorithm, which is a screening method that uses several measurements and factors to estimate risk.
  • Be classified as high risk for preeclampsia on that screening.
  • Give voluntary informed consent, meaning agree freely and sign the consent form.
  • Be willing to follow the study protocol, including taking aspirin (ASA), having extra blood tests and ultrasounds, and following the treatment plan assigned at randomization, which means the treatment group is chosen by chance.

Who cannot join the trial?

4 criteria

  • Pregnancy loss early in pregnancy, a stillbirth (when the baby dies before birth), or a fetus with a major malformation (a serious problem in how the baby is formed).
  • A fetus with a known genetic disease or chromosomal disease (a condition caused by a change in genes or chromosomes).
  • A medical reason that makes aspirin unsafe to use, including a known allergy to aspirin or not being able to tolerate it because it causes harmful side effects.
  • Being unable to stop aspirin when required, such as in antiphospholipid syndrome (a condition in which the immune system increases the risk of blood clots and pregnancy problems).
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Investigated drugs

Aspirin is the medicine being tested in this study. It is taken by mouth and is being used to help prevent preeclampsia, a pregnancy complication that can affect the mother’s blood pressure and the baby’s growth. In this trial, the researchers are studying whether stopping aspirin earlier in pregnancy works as well as continuing it later on to lower the risk of preterm preeclampsia.

What is already known about the treatment

Acetylsalicylic acid - Acetylsalicylic acid is usually taken by mouth as a tablet, and in this trial it is given orally at a dose of 150 mg. It is a well-known medicine that is widely used in medical practice and is also strongly supported in medical literature, especially for low-dose use in pregnancy to help prevent preeclampsia. Its main uses include preventing blood clots, reducing pain and fever at higher doses, and lowering the risk of preeclampsia in pregnant people at risk. It works by blocking an enzyme called cyclooxygenase, which lowers the making of substances that cause clotting, pain, and inflammation, and it is classified as a non-steroidal anti-inflammatory drug and an antiplatelet medicine.

Investigated diseases

Preeclampsia - Preeclampsia is a pregnancy-related disorder marked by high blood pressure that develops after 20 weeks of pregnancy and is often accompanied by signs that the body is under stress, such as swelling or protein in the urine. It usually begins after a period of normal pregnancy and can appear gradually or more suddenly. In some cases, it progresses to a more severe form with worsening blood pressure and broader effects on the mother’s organs and the baby’s growth.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase ITrial ID2025-524646-94-00Protocol codeOptim-PRE26Estimated enrolment16 836 patientsSponsorFundacio Hospital Universitari Vall D’Hebron Institut De Recerca

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