Aspirin (Acetylsalicylic acid) during pregnancy

Is aspirin or acetylsalicylic acid safe during pregnancy?

Acetylsalicylic acid (ASA, e.g. aspirin) belongs to the group of non-steroidal anti-inflammatory drugs (NSAIDs). These medications are commonly used to treat pain, fever, or cold symptoms. As a general rule, NSAIDs should be avoided during the first and third trimesters of pregnancy. For similar symptoms during pregnancy, paracetamol is usually the drug of choice.

An important exception is low-dose aspirin or low-dose acetylsalicylic acid, which is specifically used to prevent preeclampsia.

Aspirin (acetylsalicylic acid) is a well-established medication for the prevention of preeclampsia during pregnancy.

Read more: Pre-eclampsia during pregnancy

Who should take aspirin or acetylsalicylic acid during pregnancy?

Acetylsalicylic acid (ASA, commonly known as aspirin) is recommended during pregnancy for women who have risk factors for preeclampsia or in whom an increased risk of preeclampsia is identified during first-trimester screening.

This screening is part of the routine first-trimester ultrasound examination, also known as the combined test. Based on ultrasound findings, maternal medical history, and blood test results – including β-hCG, PAPP-A, and sometimes PlGF – a specialized algorithm calculates the risk of chromosomal abnormalities as well as the risk of developing preeclampsia.

If the calculated risk exceeds 1:150, supplementation with 150 mg of aspirin or acetylsalicylic acid daily is recommended.

Aspirin (acetylsalicylic acid) is also recommended for pregnant women who:

• have chronic hypertension
• have type 1 or type 2 diabetes
• suffer from chronic kidney disease
• had hypertension or preeclampsia in previous pregnancies
• have autoimmune diseases such as lupus or antiphospholipid syndrome

When can aspirin be used during pregnancy?

It is very important that prophylaxis begins before the 16th week of pregnancy, while the placenta and blood vessels are still developing. Aspirin or acetylsalicylic acid is usually continued until the 36th week of pregnancy or until preeclampsia is diagnosed. This preventive treatment is considered effective in approximately 80% of cases [1].

How is aspirin taken during pregnancy?

Aspirin or acetylsalicylic acid should only be taken by pregnant women on the recommendation of their gynecologist. Self-medication during pregnancy should be avoided.

For the prevention of preeclampsia, it is recommended to take 150 mg of aspirin (acetylsalicylic acid) once daily, preferably in the evening before bedtime. Treatment should begin before the 16th week of pregnancy (ideally around week 12) and continue until the 36th week of pregnancy.

[1] Rolnik DL, Wright D, Poon LC, et al. Aspirin versus placebo in pregnancies at high risk for preterm preeclampsia. N Engl J Med.