Antiphospholipid Syndrome (APS)

Antiphospholipid Syndrome (previously known as Hughes Syndrome) is usually associated with recurrent miscarriage, but it can also cause other pregnancy complications. It is diagnosed by specific blood tests.

When a woman has three or more miscarriages in a row, this is known as recurrent miscarriage. At least 15% of recurrent miscarriages occur as a result of APS, and it is now recognised as the most common, treatable cause of early pregnancy loss. With correct diagnosis and treatment, the pregnancy success rate has risen from just 20% before 1990 to over 80% today.

Some women have obstetric-only APS and do not display any other symptoms of the condition, other than in pregnancy. However, if you have already been diagnosed with APS and are being treated with Warfarin, it is important that you are prepared to change your treatment plan to daily Heparin injections, ideally before the embryo is six weeks old, as Warfarin is potentially harmful to your baby.

As APS pregnancies are classed as high risk, it is best to try and find a specialised or early pregnancy unit where doctors have prior clinical experience of managing APS pregnancies.

Pregnancy loss

Early pregnancy loss

The majority of miscarriages in women with APS occur at the early stages of pregnancy in the first 13 weeks.

The antiphospholipid antibodies (aPL) cause early miscarriages because they prevent the pregnancy from embedding properly in the womb, and inhibit the growth of the early foetal cells. Some women who have very early recurrent miscarriages can sometimes be labelled as infertile.

Sadly, losing a baby in early pregnancy is quite common, with about one in five of all pregnancies ending in miscarriage. As there can be many other possible causes for early miscarriage, women will not currently be tested for antiphospholipid antibodies (aPL) until they have had three miscarriages in a row.

Late pregnancy loss

Losing a baby in the second and third trimesters (from 14 weeks until birth) is, thankfully, rare in most pregnancies, but is unfortunately very strongly associated with APS, with many losses occurring between three and six months. Therefore, it is important that any woman with late pregnancy loss should be tested for antiphospholipid antibodies (aPL).

The antibodies act in a different way in later pregnancy loss than with early miscarriage, by causing clots in the small and delicate veins in the placenta. The placenta is then unable to supply the baby with nutrients and oxygen so it stops growing and, sadly, dies.


If you have suffered early miscarriages, occurring before 13 weeks, the treatment plan will usually involve taking low dose of Aspirin (75mg-150mg) every day. It is also usual to combine this with daily Heparin injections, particularly if you have had a later loss or you have had previous pregnancy complications such as pre-eclampsia. You will be shown how to inject yourself at the clinic, then will have to do this yourself throughout the rest of the pregnancy, until your specialist tells you it is time to stop. It is now common to stop the heparin injections a few weeks before the birth, but you will need to speak to your doctor as every pregnancy is unique.

Possible complications


Pre-eclampsia affects up to 10% of all pregnancies, but it is twice as likely to occur in women with APS, begins at an earlier stage and is more severe. It is now thought that pre-eclampsia is caused by a lack of blood being supplied to the placenta. As antiphospholipid antibodies (aPL) can damage the placenta by causing clots in the small vessels, it is likely this is why it is so common among women with APS. Pre-eclampsia if untreated, can lead to serious complications including placental abruption. It is currently diagnosed from blood and urine tests, but there is a new, very accurate, test which may be available in the future. If you do have severe pre-eclampsia, you will have to be looked after in hospital to receive medication to lower the blood pressure and control the symptoms. The only way to cure pre-eclampsia is to deliver the baby so, in many cases, labour has to be induced and your baby will be born prematurely,

Intrauterine growth restriction (IUGR)

Intrauterine growth restriction (IUGR) refers to the reduced growth of a baby while in the womb. It is estimated to affect between 10-30% of babies born to mothers with APS. When you have a high risk APS pregnancy, you will have Doppler ultrasound scans to discover if there is a fall in fetal blood supply. If there is a problem, the scan can help the specialists decide whether to move towards an earlier (possibly caesarean) delivery.

Is APS hereditary?

As of yet, there have been no wide-scale studies looking into whether APS is hereditary or if there is a genetic connection. However, there is a small amount of anecdotal evidence which does indicate that the condition can run in some families, but not all. APS Support UK advises that if either parent has a positive test and you are concerned that your child is displaying symptoms, or your daughter intends to go on the contraceptive pill or is planning a pregnancy, you should have your child tested.


Patients UK

APS Action

The Lancet 2010

The BMJ 2010


With thanks

In partnership with APS Support UK