Recurrent Miscarriage: What Testing Can and Cannot Tell You

The honest picture, with numbers

Recurrent miscarriage is defined in the UK as three or more early miscarriages, and the RCOG puts it at 1 in 100 women — about 1% of couples. The losses do not have to be consecutive, and healthy pregnancies in between do not reset the count.

The most common single explanation for any miscarriage, and for recurrent miscarriage, is that the pregnancy developed with the wrong number of chromosomes. The RCOG puts this at 1 in 2 (50%) of miscarriages, and it becomes more common as parents get older. In most of those cases both parents have entirely normal chromosomes. In about 6 in 100 couples who have had three miscarriages, one parent carries their own chromosomes in an unusual arrangement — a balanced rearrangement that causes them no symptoms but can be passed on in an unbalanced form.

Age is the strongest single predictor. The RCOG's figures for the risk of miscarriage in any one pregnancy:

Here is the number most people are looking for, and it is better than expected. Tommy's states that where no cause for recurrent miscarriage has been found, 75 in 100 couples will have a successful pregnancy with supportive antenatal care. Tommy's Net, the research database run with the National Centre for Miscarriage Research, followed the first 777 women attending recurrent miscarriage clinics and found that within two years of their first clinic visit, 6 in 10 went on to have a pregnancy lasting beyond 24 weeks. ACOG, which uses a two-loss definition, puts the figure at about 65 in 100 women with unexplained recurrent pregnancy loss having a successful next pregnancy.

None of those numbers make the losses smaller. They are here because the question "is it worth trying again" deserves an answer with data in it rather than encouragement.

What testing looks for, and what it can tell you

About half of people will get no answer after all the testing is done. That is the single most important thing to know before you start, because a normal result set is a common outcome rather than a sign that something was missed.

Blood tests

• Antiphospholipid syndrome (APS). This is the one clearly treatable cause. Diagnosis requires positive results on two blood tests at least 12 weeks apart, and at least 6 weeks after a miscarriage. A single positive is not a diagnosis.
• Thyroid function and thyroid antibodies. Well-controlled thyroid disease does not cause miscarriage, but a high TSH or the presence of thyroid antibodies is associated with higher risk.
• Diabetes testing where the history suggests it. Well-controlled diabetes does not increase risk; poorly controlled diabetes does.
• Prolactin and PCOS screening where there are pointers to a hormonal cause.
• Inherited thrombophilia testing is not recommended — the RCOG states there is no clear evidence these cause recurrent miscarriage.

Genetic tests

At the time of a third or further miscarriage, you should be offered testing of the pregnancy tissue for chromosomal problems. Both partners may be offered karyotyping if the pregnancy could not be tested, or if testing suggests the problem could be inherited. If a rearrangement is found in either partner, genetic counselling should follow.

A scan of the uterus

You should be offered a pelvic ultrasound to look at the shape of the uterus. Around 5 to 6 in 100 women are born with a congenital uterine anomaly; among women with recurrent miscarriage the figure is around 13 in 100. A uterine septum may be offered surgical correction. Whether surgery for fibroids or other internal changes reduces miscarriage risk is genuinely not known.

Sperm testing

The RCOG notes that abnormal DNA in sperm may be associated with recurrent miscarriage, but that there is no good evidence that sperm health can be changed to reduce the risk — and therefore sperm testing is not usually offered. If a private clinic offers you a sperm DNA fragmentation test as a route to recurrent miscarriage treatment, that is the context to hold it in.

What treatment there is, honestly stated

• APS: low-dose aspirin plus heparin injections in pregnancy increases the chance of a successful pregnancy. Pregnancy is then monitored closely.
• Low-dose aspirin on its own for unexplained recurrent miscarriage is not recommended by Tommy's, which notes current evidence suggests it is not beneficial and may be harmful.
• Progesterone: there is no evidence it prevents recurrent miscarriage in general. Where you have miscarried before and are bleeding in early pregnancy, progesterone should be offered. Tommy's quantifies the benefit: roughly 5% higher chance after 1 or 2 previous miscarriages, roughly 15% after 3 or more.
• Uterine septum: surgical correction may be offered.
• Unexplained recurrent miscarriage: the RCOG states there is currently no evidence that any form of medical treatment reduces the chance of a further miscarriage. What does appear to help is supportive care from a team experienced in recurrent miscarriage, including early reassurance scans.

Tommy's cites research on more than 300 women with recurrent miscarriage showing that seeing a heartbeat at 6 weeks was associated with a 78% chance of the pregnancy continuing, rising to 98% at 8 weeks and 99.4% at 10 weeks. That is why early scanning is offered — not because it changes the outcome, but because each scan meaningfully narrows the uncertainty you are carrying.

When to seek help, and where

In the UK, talk to your GP after three miscarriages; NHS guidance is that you will usually be referred for tests and offered support. The RCOG's advice is that you and your partner should be seen together where possible, and that investigations may be arranged in a clinic dedicated to recurrent miscarriage.

Do not wait for a threshold if you are struggling with your mental health. Anxiety, depression and post-traumatic stress after pregnancy loss are common and treatable, and the RCOG explicitly says you can be referred for further support.

Support that exists right now

• Miscarriage UK (formerly the Miscarriage Association) — helpline 0303 003 6464, open Monday, Tuesday and Thursday 9am–4pm and Wednesday and Friday 9am–8pm, plus online chat. Their site is at miscarriageuk.org.
• Tommy's — free midwives' helpline on 0800 0147 800, 9am–5pm Monday to Friday, staffed by midwives trained in bereavement support. Tommy's also runs a personalised Miscarriage Support Tool.
• NHS talking therapies — you can refer yourself directly in England, without going through a GP.
• Some recurrent miscarriage clinics have bereavement counselling attached. Ask what is available where you are.

One last thing worth saying plainly, because it is the thing people carry longest: as ACOG puts it, miscarriages are almost never caused by anything you did or did not do.