Aspirin and calcium during pregnancy?

In our practice, some women are advised to take a low dose of aspirin and extra calcium daily during pregnancy. This often raises questions: Why aspirin and calcium? Is it safe for my baby? And do I really need it?

In this article, we explain why aspirin and calcium are prescribed in certain cases, how they work, and for which risk factors their use is beneficial. This helps you understand exactly what this advice is based on — so you can make a well-informed choice with confidence.

Who is advised to take aspirin + calcium?

We look at the risk factors in your medical and family history. We distinguish between:

High-risk factors:

• Previous pre-eclampsia (high blood pressure with protein in the urine — also called pregnancy toxemia or HELLP syndrome)
• High blood pressure before pregnancy
• Type 1 or type 2 diabetes
• Chronic kidney disease
• Autoimmune disorders such as SLE or APS
• Previous baby with severely low birth weight

Moderate-risk factors (two or more):

• First pregnancy
• Age over 40
• More than 10 years since a previous pregnancy
• Family history of pre-eclampsia (pregnancy toxemia)
• Overweight (BMI > 35)
• Twin pregnancy
• Placental insufficiency (poor placental function in a previous pregnancy)
• Pregnancy after egg donation

If you have one high-risk or two moderate-risk factors, we recommend taking aspirin + calcium. That means you have a slightly higher chance of complications during pregnancy than average, such as:

• Pre-eclampsia: a combination of high blood pressure and protein in the urine. This is also known as pregnancy toxemia, or in severe cases, HELLP syndrome.
• Growth restriction of your baby: your baby is smaller than expected for the stage of pregnancy.

These conditions develop when the placenta does not form properly. Aspirin helps support healthy placental development, while calcium may have a protective effect on the placental endothelium (the inner lining of the placenta). Research shows that starting aspirin before the 16th week of pregnancy can reduce the risk of these complications.

It’s important to know that aspirin and calcium lower the risk, but do not eliminate it completely. They don’t prevent pre-eclampsia or growth restriction in everyone — but they do improve your chances of a healthy pregnancy.

Summary

• Aspirin (acetylsalicylic acid) and calcium can reduce the risk of pre-eclampsia and growth restriction in your baby.
• They are most effective when started early — ideally before 16 weeks of pregnancy.
• Not everyone needs aspirin: it’s recommended only when there’s an increased risk of certain complications.
• The aspirin dose is low (100 mg per day) and is safe for both you and your baby.
• Possible side effects include stomach discomfort; contact us or your doctor if this occurs.
• Never start taking aspirin or calcium without consulting us or your doctor first!

How to use aspirin safely

• Start early: before the 16th week of pregnancy.
• Dosage: 100 mg per day.
• Do not take (or only in consultation) if you have or have had gastrointestinal disease (such as Crohn’s or ulcerative colitis), low platelet counts, severe heart failure, hypersensitivity to acetylsalicylic acid, or asthma attacks triggered by aspirin use.
• Important: If you use an SSRI, stomach protection is required.
• Where to buy: Available at pharmacies or drugstores. Make sure to buy Aspirin labeled “Acetylsalicylic acid 100 mg.”
• How to take: Preferably in the evening with water, while sitting upright.
• When to stop: Around the 36th week of pregnancy, or earlier if labor starts.
• Safety: Aspirin is safe for both you and your baby. It does not increase the risk of birth defects or excessive bleeding.

Note: If you’ve ever had a stomach ulcer, stomach bleeding, or an allergy to aspirin, please discuss this with us before starting.

How to use calcium safely

• Start early: before the 16th week of pregnancy.
• Dosage: 1000 mg calcium per day.
• Do not take (or only in consultation) if you have severe kidney disease, hyperphosphatemia, severe hypercalciuria, kidney stones, or hypercalcemia.
• Where to buy: Available at pharmacies or drugstores. If you take a prenatal multivitamin, check how much calcium it contains — often not enough — so an additional supplement may be needed.
• How to take: Once daily; time of day doesn’t matter.
• When to stop: After delivery.
• Safety: Calcium is safe for both you and your baby.

Frequently Asked Questions

I want to read more about this

You can!

• www.degynaecoloog.nl
• Protocol OLVG
• www.ncbi.nlm.nih.gov
• www.esht.nhs.uk
• www.guysandstthomas.nhs.uk

What if I get stomach problems from aspirin? That can happen. It often helps to take the medication with some food. Sometimes a stomach protector such as omeprazole is needed. If you experience symptoms, please contact us. Does aspirin really help prevent complications? Yes, studies show that it reduces the risk of pre-eclampsia and growth restriction. It’s not a guarantee, but it lowers the likelihood of complications. Is it dangerous for my baby? No, low-dose aspirin is safe during pregnancy. What if I accidentally skip a day? No worries. Just take your regular dose the next day. Don’t take two pills at once to make up for it. I don’t have an increased risk. Should I still take extra calcium? Yes! All pregnant women are advised to take 1000 mg of calcium per day from 20 weeks of pregnancy onward. For women with a higher risk of severe high blood pressure, we recommend starting calcium from the beginning of pregnancy.

That can happen. It often helps to take the medication with some food. Sometimes a stomach protector such as omeprazole is needed. If you experience symptoms, please contact us.

Does aspirin really help prevent complications?

Yes, studies show that it reduces the risk of pre-eclampsia and growth restriction. It’s not a guarantee, but it lowers the likelihood of complications.

Is it dangerous for my baby?

No, low-dose aspirin is safe during pregnancy.

What if I accidentally skip a day?

No worries. Just take your regular dose the next day. Don’t take two pills at once to make up for it.

I don’t have an increased risk. Should I still take extra calcium?

Yes! All pregnant women are advised to take 1000 mg of calcium per day from 20 weeks of pregnancy onward. For women with a higher risk of severe high blood pressure, we recommend starting calcium from the beginning of pregnancy.

I read about different aspirin dosages

In (international) literature, different aspirin dosages are mentioned, ranging from 80 to 150 mg per day. In the Netherlands, the recommended dosage is 100 mg per day.