Antiphospholipid Syndrome (APS)

Antiphospholipid syndrome is an immune system disorder that increases the risk of blood clots. It’s sometimes known as Hughes syndrome.

If you have APS, you have a higher risk of developing:

  • deep vein thrombosis (DVT), which is a blood clot that usually develops in the leg
  • arterial thrombosis (a clot in an artery), which can cause a stroke or heart attack
  • blood clots in the brain, which can lead to problems with balance, mobility, vision, speech and memory.

Antiphospholipid Syndrome Information

How can antiphospholipid syndrome affect pregnancy?

APS has also been linked to pregnancy complications, including:

  • recurrent miscarriage
  • late miscarriage (a miscarriage that happens after the first 12 weeks of pregnancy)
  • stillbirth
  • premature birth
  • pre-eclampsia
  • placental complications
  • fetal growth restriction.

This sounds scary but try to remember that APS is treatable. With the right treatment and care, most women with APS have successful pregnancies. APS is also one of the most treatable causes of recurrent miscarriage.

If you need emotional support...

Don’t hide your feelings or suffer in silence. You are not alone. Tell you partner, family or friends how you feel. Your GP can help you access any professional support you need, and the charity APS Support UK may also be able to help.

How is APS in pregnancy treated?

Is there a cure?

Unfortunately, there is no cure for APS. Treatment in pregnancy will focus on keeping you and your baby healthy by reducing the risk of complications as much as possible.

If you haven’t been diagnosed with APS

If you’ve had recurrent or late miscarriages, you may be able to get referred for tests to try and find out why. This may include a test for APS.

Your doctor will talk to you about your medical history. They will ask if you’ve had:

  • 1 or more confirmed blood clots
  • 1 or more unexplained late miscarriage at or after week 10 of your pregnancy
  • 1 or more premature births at or before week 34 of your pregnancy
  • 3 or more unexplained early miscarriages before week 10 of your pregnancy.
  • You’ll also have a blood test to look for the abnormal antiphospholipid antibodies that increase the risk of blood clots. If you have 2 abnormal blood test results, with at least a 12-week gap between them, you’ll be diagnosed with APS.

If you have been diagnosed with APS before you get pregnant

The best thing you can do is speak to your GP or specialist before you get pregnant. This is because the treatment needed to give you the best chance of a successful pregnancy is most effective when it starts as soon as possible. Some medications used to treat APS can also harm an unborn baby, so your doctor will want to review your medication before you get pregnant. Do not stop taking any medication before seeing your doctor.

Sometimes things don’t go to plan. If you have APS and did not speak to your healthcare professional before getting pregnant, try not to worry. Speak to your GP or specialist as soon as possible.

Your care during pregnancy

Because of the risk of complications such as pre-eclampsia and intrauterine growth restriction, you should be carefully monitored throughout pregnancy.

You will be treated as a high-risk pregnancy and will have tailor-made care, based on your own individual medical and pregnancy history and risk factors.

Your care will be doctor-led, although you will still have care from the midwifery team too. It’s likely that you will have more blood, urine and blood pressure checks than usual. You will also have additional scans to check your baby’s growth, as well as the blood flow through the placenta and cord to your baby.

It can be stressful to have more tests and antenatal appointments than expected in an uncomplicated pregnancy. But this extra care will help your healthcare professionals make sure that you have a safe and successful pregnancy.


You’ll be asked to take daily doses of aspirin or heparin, or a combination of both. These medications make your blood less likely to clot and are safe to take in pregnancy.

Warfarin isn’t recommended during pregnancy because it carries a small risk of causing birth defects. However, if you are taking warfarin to prevent clotting it is not safe to stop. It must be changed to an alternative anti-clotting drug, which is usually heparin. Speak to your GP or specialist as soon as possible so your medication can be changed safely.

Reducing the risk of blood clots in pregnancy

What can you do?

There are some things you can do to reduce your risk of developing blood clots and improve your chance of having a healthy pregnancy and baby. These include:

  • not smoking
  • eating a healthy, balanced diet
  • exercising regularly.
  • Because you have a higher risk, you will be checked regularly for pre-eclampsia and blood clots.

Symptoms of a blood clot

  • throbbing or cramping pain, swelling, redness and warmth in a leg or arm (it may feel like a hot patch)
  • sudden breathlessness, sharp chest pain (may be worse when you breathe in) and a cough or coughing up blood.
  • Contact your midwife, doctor or NHS 111 straight away if you think you have a blood clot.

The Birth and APS

Your baby’s movements and APS

Because there is a higher risk of stillbirth, it’s also important to be aware of your baby’s movements during your pregnancy. Your baby will have their own pattern of movements that you should get to know. You should continue to feel your baby move right up to the time you go into labour and during labour.

Contact your midwife or maternity unit immediately if you think your baby’s movements have slowed down, stopped or changed.

Can APS affect how I give birth?

If you and your baby are healthy, it is possible to have a vaginal delivery. Your healthcare team may recommend having Electronic Fetal Monitoring (EFM). This involves being attached to a monitor that continuously monitors your baby’s heartbeat and your contractions.

If there are any concerns about you or your baby’s health you may need a caesarean section.

After the birth if you have APS

You may need to keep taking medication for a few weeks after giving birth to help prevent blood clots.

Your fertility after the birth

You can get pregnant 3 weeks after you’ve given birth, even if you’re breastfeeding and your periods haven’t started again.

If you want to have another baby, the best thing to do is speak to your GP or specialist about when is safe time for you to start trying. It’s important to use contraception every time you have sex until you have spoken to your healthcare professional.

Not all contraceptives are suitable for all women after giving birth. Because you are at risk of blood clots, you should not use the following until at least 6 six weeks after birth:

  • combined pill
  • vaginal ring
  • contraceptive patch.

Speak to your midwife, GP or health visitor for more information.

More support and information
APS Support UK provides support to anyone affected by APS in the UK. Their website includes factsheets about living with APS and details of specialists in your area (all referrals must go through your GP).

Last reviewed: January 2021