Obstetric & Gynaecology Malaysia


Aspirin is also known as acetylsalicylic acid. It is a common prescription and over-the-counter medication similar to non-steroidal inflammatory (NSAIDs) like ibuprofen (e.g.Advil) and naproxen (e.g., Aleve, Synflex) that reduces inflammation, fever, and pain.


 can prevent the formation of blood clots. This can make aspirin useful in treating or preventing some conditions like heart attacks and strokes. Low-dose aspirin ranges from 60-150 mg daily.

Regular strength aspirin is NOT a preferred pain reliever during pregnancy.


When should I start taking low-dose aspirin?

You should start taking low-dose aspirin between weeks 12 and 16 of your pregnancy.

The USPSTF guidelines recommend starting between weeks 12 and 28 of your pregnancy, recent evidence shows that starting closer to the beginning of your second trimester may be more beneficial.

A review of 45 randomized trials that included over 20,000 pregnant women taking daily low-dose aspirin showed significant evidence of the prevention of preeclampsia, severe preeclampsia, and fetal growth restriction d/t placental insufficiency when initiated before 16 weeks’ gestation. Low-dose aspirin initiated after 16 weeks’ gestation may not be as effective at reducing the risk of preeclampsia, severe preeclampsia, and fetal growth restriction. 

Who are those women at pregnancy risk that can be identified in early pregnancy?

High risk-

1. History of preeclampsia. 2. Twin pregnancy. 3. Chronic hypertension. 4. Diabetes. 5. Renal disease (eGFR< 6o or proteinuria). 6. Autoimmune disease (systemic lupus erythematous, antiphospholipid syndrome).

Moderate risk-

 1. Nulliparity (never having given birth). 2. Obesity (body mass index >27.5 kg/m2). 3. Family history of preeclampsia (mother or sister). 4. Sociodemographic characteristics (smoker, low socioeconomic status). 5. Age ≥35 years. 6. Personal history factors (e.g., low birthweight or small for gestational age, previous adverse pregnancy outcome, >10-year pregnancy interval)

Does it matter what time of day I take my dose?

Yes! Research shows that aspirin is most effective at bedtime.

What are the risks associated with taking prenatal aspirin?

The USPSTF report found:

  • No increase in infant loss, growth problems, or cognition harm to the baby;
  • No statistically significant impact on risk of placental abruptions, postpartum hemorrhage (bleeding), or miscarriage to the mother;
  • No differences in developmental outcomes of the infants up to age 18 months.

No studies have followed the offspring of preeclamptic women on aspirin beyond 18 months.
If your doctor decides to put you on aspirin, she is doing so because she feels that the potential benefits greatly outweigh the minimal risks.

Can taking low-dose aspirin increase my risk of miscarriage?

Taking low doses of aspirin is not thought to increase the risk of miscarriage. Research suggests the use of aspirin during pregnancy is not associated with an increased risk of miscarriage.

Will aspirin hurt the baby?

Studies on the effects of low-dose aspirin on fetal and maternal health and development are reassuring, and low doses of aspirin administered during the first trimester do not seem to constitute risk for the fetus.

When should I stop taking low-dose aspirin?

It is very important that you ask your doctor when you should stop taking aspirin, as recommendations may be differ depending on your medical history.

There are opposing arguments regarding when to discontinue aspirin treatment. Some argue that aspirin should be discontinued at 36 weeks because of the possible bleeding risks associated with delivery.

Others argue, because most preeclampsia occurs after 36 weeks, that the aspirin may be beneficial to continue through delivery, into the postpartum period.

Do I need to consult a healthcare provider before starting low-dose aspirin?

Yes. Only women at high risk or with 2 or more moderate risk factors for preeclampsia should consider low-dose aspirin. For that reason, the pregnancy should be closely monitored.Treatment with low-dose aspirin in high-risk patients should not decrease regular monitoring and response by a doctor. If you experience signs or symptoms of preeclampsia, notify your healthcare provider immediately. 

Does taking aspirin guarantee that preeclampsia will be prevented or delayed?

Taking aspirin does not guarantee that you will not develop preeclampsia. It is simply one more thing that women can do with relative safety to reduce their overall risk. The USPSTF review took into account approximately 30,000 randomized subjects, which found a 2 to 5% risk reduction in the rate of preeclampsia. Both the USPSTF and ACOG acknowledge that tools to assess individual risk for the condition and identify subgroups of mothers most likely to benefit are still needed.
The USPSTF authors also agreed that preventing preeclampsia could reduce medical intervention in pregnancy and delivery. Preventing poor pregnancy outcomes could also reduce post-traumatic stress disorder and postpartum depression because preeclampsia is associated with poor maternal mental health outcomes.

Taking low doses of aspirin is not thought to increase the chance of miscarriage. Some studies have shown that taking low dose aspirin before conceiving may actually help lower the chance of miscarriage in some people who have had one or more previous miscarriages before 20 weeks of pregnancy.

A daily low dose of aspirin does not appear to prevent subsequent pregnancy loss among women with a history of one or two prior pregnancy losses, according to researchers at the National Institutes of Health.

However, in a smaller group of women who had experienced a single recent pregnancy loss, aspirin increased the likelihood of becoming pregnant and having a live birth.