If you are reading this after losing more than one pregnancy, we are sorry. Being told it is probably just bad luck can feel dismissive when it keeps happening. This guide sets out what is known about recurrent miscarriage causes, which tests you should be offered, what treatment exists once something is found, and what the evidence says about your chances next time.
One thing before the clinical detail: you do not have to wait for tests to talk to someone. Our fertility counselling service is open to you at any stage, whether or not you go on to have investigations with us.
What counts as recurrent miscarriage?
In the UK, recurrent miscarriage is usually defined as three or more miscarriages in the first trimester (before 13 weeks). The losses do not need to have been consecutive, and they do not need to have been with the same partner. A single loss in the second trimester (after 13 weeks) is investigated in its own right, without waiting for it to happen again.
The 2023 RCOG Green-top Guideline also recognises that three is not a magic number. It encourages specialists to investigate after two first-trimester losses where there is reason to think something underlying is at work, for example if you are 38 or older, if the losses happened after a heartbeat was seen, or if there is a relevant medical or family history. At Aurora we take that approach: if you have had two losses and want answers, you do not need to go through a third before anyone looks.
How common is it?
Miscarriage itself is common. The NHS estimates that around one in eight pregnancies where the woman knows she is pregnant ends in miscarriage, and the true figure is higher because many losses happen before a period is missed. Most are one-off events caused by a random chromosomal error in the embryo, which is why the risk rises with age: roughly one in ten pregnancies in the early twenties, climbing to around half or more by 45.
Recurrent miscarriage is much rarer. Around one in 100 women who try for a baby will have three or more losses, and around one in 20 will have two. Those numbers are higher than chance alone would predict, which is why investigation is worthwhile: in a proportion of couples there is a specific, often treatable, reason.
The known causes
In roughly half of the couples who are fully investigated, a contributing cause is identified. These are the ones that matter most, in the order a specialist would think about them.
Chromosomal and genetic factors
Most individual miscarriages are caused by a chromosomal abnormality in that pregnancy, arising by chance at conception. With repeated losses the question is different: in around two to five per cent of couples with recurrent miscarriage, one partner carries a rearrangement of their own chromosomes, called a balanced translocation. It causes them no health problems, but it can produce embryos with too much or too little genetic material. This is why testing the pregnancy tissue itself is now the preferred first step, with blood tests on the parents only if the result points that way.
Uterine structure, fibroids and adhesions
The shape of the womb affects how an early pregnancy implants and grows. A septum (a band of tissue dividing the cavity), uterine fibroids that push into the cavity, polyps, and scar tissue (adhesions) from previous surgery or infection are all more common in women with recurrent loss than in the general population. A weakness in the cervix is a separate issue and is mainly linked to losses in the second trimester rather than early miscarriage.
Hormonal and thyroid factors
An underactive thyroid that is not being treated, thyroid antibodies, poorly controlled diabetes and a raised prolactin level can all increase the chance of miscarriage, and the first two are now routinely checked. Polycystic ovary syndrome is associated with a somewhat higher early loss rate, probably through insulin resistance; we covered that in more detail in our guide to PCOS and fertility.
Blood clotting and immune factors
Antiphospholipid syndrome (APS) is the most important treatable cause of recurrent miscarriage and is found in around 15 per cent of women investigated. It is an autoimmune condition in which antibodies make the blood more likely to clot, interfering with the placenta as it forms. Inherited clotting tendencies (thrombophilias such as Factor V Leiden) were tested for routinely in the past, but the current RCOG guidance no longer recommends this for early recurrent miscarriage because treating them has not been shown to help. The same applies to natural killer cell tests, which are no longer recommended.
For about half of couples, every test comes back normal. That is a frustrating result, but it is not a hopeless one. Unexplained recurrent miscarriage has one of the better outlooks of all the groups, as the figures below show, and normal results close off the treatable causes so the plan for your next pregnancy can focus on support and early monitoring.
What tests should you be offered?
The RCOG guideline recommends a graded approach: information and support after a first loss, initial screening after two, and full consultant-led investigation after three or after any second-trimester loss. A complete recurrent miscarriage testing panel includes:
- Antiphospholipid antibody tests. Blood tests for lupus anticoagulant, anticardiolipin antibodies and anti-beta-2 glycoprotein I antibodies. A positive result is repeated at least 12 weeks later, because a single raised reading can be a temporary response to the loss itself.
- Thyroid function and thyroid antibodies. TSH and thyroid peroxidase (TPO) antibodies.
- A detailed pelvic ultrasound, ideally in 3D, to assess the shape of the womb cavity and the ovaries, followed where needed by an outpatient hydrosonography (a scan with a small amount of fluid in the womb) or a hysteroscopy to look at the cavity directly.
- Genetic testing of the pregnancy tissue from the third and any later loss, and from any second-trimester loss. If an unbalanced chromosome rearrangement is found, both partners are offered a blood karyotype.
- A general hormonal screen where your history suggests it, for example irregular cycles, PCOS or symptoms of raised prolactin.
- For second-trimester losses, an assessment of the cervix and consideration of inherited thrombophilia testing, which is relevant to late loss in a way it is not to early loss.
Our recurrent miscarriage care covers this panel in a consultant-led pathway, with the results drawn together into a single plan rather than left for you to piece together. If your losses have followed IVF, we would also look at the embryo and uterine factors covered by our implantation failure service, because the two overlap.
What treatment is available once a cause is identified?
Treatment follows the cause. The table shows what the evidence currently supports.
| Cause | Treatment | What the evidence says |
|---|---|---|
| Antiphospholipid syndrome | Low-dose aspirin plus heparin injections from a positive pregnancy test | The best-supported treatment in recurrent miscarriage. Live birth rates improve substantially compared with no treatment. |
| Underactive thyroid | Levothyroxine, with thyroid function checked again in early pregnancy | Clearly beneficial where the thyroid is underactive. Women with normal thyroid function but positive antibodies are not treated, as the TABLET trial showed no benefit. |
| Septum, fibroids, polyps or adhesions in the cavity | Hysteroscopic surgery, usually as a day case | Reasonable to offer after discussion. The evidence for septum removal is weaker than it once seemed, so the decision is individual. |
| Cervical weakness (late loss) | A cervical stitch (cerclage) in pregnancy, or laparoscopic cerclage placed between pregnancies | Effective in well-selected women with a history of painless late loss or very early delivery. |
| Balanced translocation | Genetic counselling; natural conception with early scans, or IVF with embryo testing (PGT-SR) | Most couples do conceive a healthy pregnancy naturally in time; embryo testing shortens the route for some. |
| Unexplained, with bleeding in early pregnancy | Vaginal micronised progesterone from the start of bleeding to 16 weeks | The PRISM trial showed a modest but real increase in live births in women with previous miscarriages and bleeding. Not shown to help without bleeding. |
Alongside any specific treatment, the steps that help everyone are stopping smoking, keeping alcohol and caffeine low, a healthy weight, folic acid and vitamin D, and early pregnancy scans so that you are not waiting alone. Treatments without good evidence, including steroids, intralipid infusions, immune therapies and heparin for women without APS, are not something we recommend, and we will say so.
What are the chances of a successful pregnancy after recurrent loss?
Better than most people fear. The large follow-up studies behind the RCOG guidance show that around three in four women with unexplained recurrent miscarriage go on to have a successful pregnancy with supportive care alone: a named clinician, early scans and someone to call. Where a cause such as APS is found and treated, the outlook is similar or better.
Two things shape that figure: age, because the chance of a chromosomal error rises each year, and the number of previous losses, each of which lowers the odds a little. A 32-year-old after three losses and a 41-year-old after five are not in the same position, and a good consultation will tell you where you sit rather than quoting an average. What the figure does mean is that, for most people reading this, the next pregnancy is more likely to succeed than not.
Getting a second opinion
Many people who come to us have already been told their results are normal, or been advised to simply try again. If that is where you are, a second opinion is a reasonable thing to ask for, and you do not need a GP referral to arrange one privately.
At Aurora, recurrent miscarriage consultations are led by Dr Edmond Edi-Osagie, Consultant Gynaecologist and Medical Director, whose specialist interests span recurrent loss, implantation failure and the gynaecological conditions (endometriosis, fibroids, uterine abnormalities) that often sit underneath it. The first appointment reviews everything done so far, so tests are not repeated unnecessarily, and fills the gaps against the current guideline. Patients travel to us from across the North West and further afield, and screening is usually completed over a small number of visits to our clinic in Cheadle.
Frequently asked questions
How many miscarriages before you get investigated?
The standard NHS threshold is three first-trimester miscarriages, or one second-trimester loss. Specialist clinics, including ours, will investigate after two where there is reason to suspect an underlying cause, or where a couple wants answers before trying again.
Can you be tested after two miscarriages rather than three?
Yes. The RCOG guideline supports investigation after two losses at the clinician’s discretion, and privately you can choose to be investigated at that point. The core tests (antiphospholipid antibodies, thyroid function and a detailed scan) are the same.
What if all my test results come back normal?
It means the treatable causes have been excluded, which is useful in itself. Most women with unexplained recurrent miscarriage have a successful next pregnancy with early scans and supportive care, and progesterone is offered if there is any bleeding.
Does age affect recurrent miscarriage risk?
Yes, mainly through egg quality. The chance that any pregnancy carries a chromosomal error rises with maternal age, and the risk also increases a little when the male partner is over 40. Age is one of the reasons we investigate after two losses rather than three in women aged 38 and over.
Can recurrent miscarriage be treated?
Where a cause is found, usually yes: aspirin and heparin for antiphospholipid syndrome, thyroid treatment, surgery for a septum or fibroids, or a cervical stitch for cervical weakness. Where no cause is found, treatment is supportive, and the outcomes with that support are good.
About the reviewer
Dr Edmond Edi-Osagie is a Consultant Gynaecologist and the Medical Director of Aurora Healthcare, with more than 20 years’ experience in assisted conception and advanced laparoscopic surgery. He established and leads the BSGE-accredited endometriosis centre at Aurora and is a Senior Lecturer in Gynaecology at the University of Manchester.
Arrange a recurrent miscarriage consultation
If you have had two or more miscarriages and want a specialist to look properly, we are here. Consultations are consultant-led, no GP referral is needed, and counselling is available alongside every step. Get in touch online or call 0161 244 8623 to book a confidential consultation.
