Recurrent Miscarriage

Recurrent miscarriage refers to having three or more miscarriages, whether or not you have had healthy pregnancies in between. Experiencing repeated loss can be particularly painful and can lead to fear and anxiety about trying again.

Medical investigations may help identify potential causes, but sometimes no clear reason is found. Regardless, each person’s feelings are valid, and ongoing emotional support is just as important as medical care.

“It’s scary to get a positive pregnancy test result now, because I might have to go through the loss and grief all over again.”

Causes of recurrent miscarriage

The causes of recurrent miscarriage are often the same as the causes of a single miscarriage. However, there are certain risk factors that make miscarriage more likely to happen more than once.

Genetic factors

About half of all early miscarriages are caused by random, ‘one-off’ errors in the egg or the sperm, or in how the fertilised egg develops. It is not always clear what causes these faults, though they are more common in women in their late 30s or older, when egg quality declines.

(Women are born with all the egg cells they will ever have, so as they age, the egg cells do too and their quality also reduces. That in turn means it can take longer to become pregnant and if there is a pregnancy, there is a higher risk of the embryo having abnormal chromosomes.)

In a very few cases, one parent has an error in the way their chromosomes are arranged, called a ‘balanced translocation’. This doesn’t cause a problem for the parent, but it can be passed on to the baby as an ‘unbalanced chromosome’ and cause a miscarriage.

Age

The risk of single and recurrent miscarriage increases with age. That is especially the case if you are over 35 and your partner (or the biological father) is over 40.

Previous miscarriages

Your risk of miscarriage increases with the number of miscarriages that you have had in the past.

Ethnicity

If you are of Black African or Black Caribbean background, you are more likely to have a miscarriage and, sadly, other pregnancy and maternity complications. Doctors do not yet know why this is and research into the possible reasons is a high priority.

Lifestyle factors

Being overweight (BMI over 25) or underweight (BMI below 18.5) increases the risk of miscarriage. There is also evidence that cigarette smoking and drinking more than the recommended maximum amount of alcohol or caffeine increases miscarriage risk.

Blood clotting problems

Antiphospholipid syndrome (APS) – also sometimes called ‘sticky blood syndrome’. Your immune system makes abnormal antibodies that can cause recurrent early miscarriage. APS can also lead to later pregnancy loss and other complications, including the baby not growing enough, pre-eclampsia or stillbirth. It also increases the risk of developing blood clots.
Inherited blood clotting problems, known as thrombophilia. Some of these, such as factor V Leiden and protein S deficiency, are linked to a slightly increased risk of miscarriage.

Abnormally shaped uterus (womb) or other uterine problems

A small number of women (5-6 in 100) are born with an unusually shaped uterus. This is rather more common (13 in 100) in women who have recurrent miscarriage.

A septate or bicornuate uterus, both divided down the centre to some extent, may increase your chance of miscarriage.
Fibroids or scar tissue in the uterus may also affect your risk of miscarriage, but this depends on their size and position.
Cervical weakness or damage. The cervix is a kind of ‘gateway’ between the uterus and the vagina. It normally dilates (widens) during labour to allow the baby to be born. If the cervix is weak or damaged, it can dilate far too early and lead to second trimester (late) miscarriage.

Hormonal problems

There are several hormonal conditions that may be connected with miscarriage.

Polycystic ovarian syndrome (PCOS) is associated with an increased risk of miscarriage. This may be due to increased levels of insulin and testosterone (male hormone) that many women with this condition have, but the relationship is not clear.
Diabetes that is well-controlled does not increase miscarriage risk. Poorly controlled diabetes may mean a higher chance of miscarriage.
Thyroid problems that are well controlled do not increase miscarriage risk. Untreated thyroid disease or high levels of thyroid stimulating hormone (TSH) or thyroid antibodies may increase miscarriage risk.
Prolactin. Abnormal levels of prolactin may increase the risk of miscarriage.

Immune factors

There is no clear evidence to show that immune problems, including raised levels of NK calls, cause or increase the risk of miscarriage. There is a need for more research in this area.

Infection

Some serious infections can cause or increase the risk of single miscarriages, but it is not clear if infection plays a role in recurrent miscarriage.

Male factors

Abnormal DNA in sperm may increase the risk of recurrent miscarriage. Age and lifestyle factors may also play a part.

Tests & Treatments

If you have had three miscarriages, you should be offered tests to see if there is an underlying reason or reasons for your losses. However, you might be offered tests after two early miscarriages, for example:

if you are in your late 30s or older, or
if it has taken you a long time to conceive, whether or not you needed fertility treatment, or
if your doctor thinks your miscarriages might have an underlying cause.

You should also be offered some tests after one second trimester loss, that is if your baby died after the first three months of pregnancy.

Types of tests

Blood tests

APS test: To confirm if you have APS you need to have positive results on two blood tests at least 12 weeks apart, and at least 6 weeks after a miscarriage.
Thyroid tests including thyroid antibody tests.
Diabetes tests if your medical history suggests this could be a factor.

Genetic tests

At the time of your third or further miscarriage, your healthcare professional should offer to test whether there were any inherited chromosomal problems causing this miscarriage.Both you and your partner may be offered genetic testing if:

it has not been possible to test the pregnancy, or
the testing of the pregnancy suggests the problem could have been inherited.

A scan of your uterus

You should be offered a pelvic ultrasound scan to look at the shape of your uterus. If your healthcare professional suspects that your uterus is an unusual shape, you may be offered further investigations to look at this in more detail.

“All the tests came back as normal. My husband was relieved as it showed that there was no obvious problem. But I was disappointed as I really wanted an answer.”

Treatments

If you are found to have a problem which has a clear treatment plan, that can be very positive news. Even so, your doctor should warn you that treatments don’t always work – especially if a pregnancy miscarries for a different reason from the one being treated. In this case, you may be encouraged to try the treatment again in another pregnancy.

Answers – or not

It’s important to know that having tests does not necessarily mean that a cause or causes will be found. About half of the couples who have investigations don’t come out with any clear reason for their miscarriages. This can be very frustrating, but it is also positive news because it means that there is a good chance of the next pregnancy being successful, without any treatment at all.

If a problem is identified, there may still be a good chance of having a successful pregnancy. This will depend on what is found and whether there is any treatment to reduce the risk next time. For example:

Some miscarriages are caused by chance (e.g. a chromosome abnormality in the baby) and cannot be predicted or prevented. Fortunately, they are not very likely to happen again.

When there are no answers

It can be very difficult to cope with not knowing why you have had repeated miscarriage and it may be hard to accept that there aren’t any answers. You might see stories in the media about a new treatment for miscarriage and there’s also a great deal of information on the internet about miscarriage causes and treatments. It can be hard to know what to trust as many investigations and treatments which are reported have not been properly studied or assessed.

Finding Support

We understand that miscarriage affects people in countless ways. Emotional responses are just as important as physical considerations, and seeking support does not mean you’re overreacting.

Whatever you’re feeling — sadness, shock, guilt, fear, or confusion — it’s valid. You don’t have to face miscarriage alone. We’re here to provide reliable information, answer questions, and support you through this difficult time.

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