The miscarriage is confirmed
Testing is only considered once a miscarriage has been confirmed using the NICE scan criteria. These call for a second specialist opinion or another scan a week or more later, sometimes both, before a diagnosis is made.
Miscarriage Confirmed but Not Yet Passed: Is Testing Still Possible?
If a scan has confirmed a miscarriage and the pregnancy is still in your womb, a blood sample may be able to show whether a chromosome change was involved. This depends on timing: the test works best before the pregnancy tissue passes or is removed.
Below we explain why the window is short, how a sample can fit around waiting, tablets or surgery, what the test can miss, and what can still be done if the miscarriage completes first. Testing is always your choice, and our genetic counsellors can help you decide.
In brief
This page in four points
- The placenta releases fragments of its DNA into your blood, and a blood test can look at them for extra or missing chromosomes.
- Those fragments fade once the pregnancy tissue has passed or been removed, so the sample is best taken, after a confirming scan, while the tissue is still in the womb.
- If the miscarriage completes first, testing the tissue, or in some situations both parents' chromosomes, may still be possible.
- Heavy bleeding, severe pain or a fever need care straight away. Testing fits around treatment, never the other way round.
How it works
Why the chance to test fades once the tissue has gone
Throughout pregnancy, cells in the developing placenta release tiny fragments of DNA into the mother's bloodstream. They carry the placenta's chromosomes, which in most pregnancies are the same as the embryo's. NIPT, the screening blood test used in ongoing pregnancies, works on the same principle.
When a pregnancy stops developing but stays in the womb, as in a missed miscarriage, placental tissue is often still in place and still releasing DNA. A laboratory can count the fragments from each chromosome and look for one that is over- or under-represented, which suggests an extra or missing chromosome.
Once the tissue has passed or been removed, the source is gone and the DNA already in your blood starts to disappear. After a birth this takes hours. After an early loss it seems to fade more gradually, but the amount drops noticeably within the first day and results become less dependable.
Think of a tap running into a basin with the plug out. While the tap is on, there is water to sample. Turn it off and the basin empties steadily. The blood test is trying to catch the water before it drains away.
The evidence on timing
What a large Danish study found about timing
Figures from El Sammaa-Aru and colleagues (Human Reproduction, 2026), who studied blood samples from 1,463 women after a pregnancy loss in Denmark. They come from one study in one country and describe groups of people, not any one pregnancy.
9 in 100 Samples that gave no result when the pregnancy tissue was still in the womb
27 in 100 Samples that gave no result when taken 12 to 24 hours after the tissue had passed
3 in 10 Samples that were inconclusive about 3 days after the tissue had passed or been removed, in a small group sampled repeatedly
4.7% vs 2.8% Median share of placental DNA in the blood less than 6 hours after the tissue passed, compared with more than 12 hours after
On the day
How the scan and the blood sample usually fit together
A scan shortly before the sample
The research studies only included pregnancies that a scan had shown to be inside the womb. A scan close to the blood test checks this and whether pregnancy tissue is still in place. It may also show a second sac (a twin or vanished twin), which can confuse the result.
Checking the test suits you
Studies left out ectopic pregnancies, pregnancies of unknown location and molar pregnancies, so the test has not been shown to work in those situations.
An ordinary blood sample
Blood is taken from a vein in your arm, as for any routine blood test, and sent to a genetics laboratory.
Treatment goes ahead, then results
Waiting, tablets or surgery continue as planned. Results are best explained by a doctor or genetic counsellor, such as one of our team, who can say whether any further test would help.
Your management options
Waiting, tablets or surgery: where a sample fits
The NICE guideline describes three ways to manage a miscarriage. A blood sample can, in principle, be taken before any of them. What differs is how predictable the timing is.
Waiting for it to happen naturally
Usually offered first, for 7 to 14 days. The tissue can come away at any point: in one UK study of missed miscarriage, about 3 in 10 had passed within a week and about 6 in 10 within two weeks. If you are considering a blood test, arrange it early.
Tablets (medical management)
For a missed miscarriage this usually means a mifepristone tablet, then misoprostol 48 hours later. Because the aim is to sample while the tissue is in place, the simplest time is before the first tablet. If you have already started, ask your care team before changing anything.
Surgery (surgical management)
Manual vacuum aspiration under local anaesthetic, or a procedure in theatre under general anaesthetic (sometimes informally called a D&C). A blood sample can be taken beforehand, and the tissue removed can also be sent for genetic testing if it is kept fresh and out of preservative.
Timing
Does a blood test hold up treatment?
A blood sample for this test is a routine procedure. Wanting the test should not, on its own, decide which way of managing the miscarriage is right for you; that rests on your health, your preferences and clinical advice. What it can affect is the order of events: to sample while the tissue is still in place, the blood has to be taken before tablets or surgery.
NHS early pregnancy units do not routinely offer this blood test, so you may need to arrange it separately. Tell the unit as soon as you know you might want testing, so that treatment and testing can be timed together rather than at the last minute.
If you feel well, NICE recommends waiting for 7 to 14 days as the first option for most people, so there is usually time to decide about treatment. The tissue can come away during that time, though, so if you are considering a blood test it is better to decide early. If heavy bleeding, severe pain or signs of infection develop, get care straight away: treatment comes first and the testing plan adapts.
If it has already happened
If the miscarriage completes before a sample is taken
Missing the window is common and is nobody's fault. Other routes may still be open.
| Your situation | What may still be possible |
|---|---|
| The tissue passed within roughly the last day | A blood sample may still work, but the chance of no result rises after about 12 hours, so ask quickly. See blood test or tissue test. |
| Tissue was collected, or removed in surgery, and kept fresh | The tissue can be tested, often with a chromosomal microarray, as long as it was not put in preservative such as formalin. Read about pregnancy tissue testing. |
| No tissue was kept and a blood test is no longer possible | Usually no further test is possible for this pregnancy. After recurrent miscarriage, both partners' chromosomes may be checked in some circumstances; see parental chromosome testing. |
| Tissue gave no result, or a 'normal female' pattern | A tissue test can fail if cells do not grow or the sample was unsuitable, and a 'normal female' result can sometimes mean the laboratory tested the mother's cells rather than the pregnancy's. See understanding your result. |
On the NHS, tissue testing is normally offered from the third miscarriage, after a second-trimester loss, or sooner if there are features suggesting a chromosome condition. After recurrent losses with no tissue result, NHS genetics guidance notes that testing any future loss is usually more informative than testing the parents.
How accurate is it?
How the blood test has performed against tissue testing
Each study compared the blood result with testing of the pregnancy tissue. Sensitivity is the share of chromosome changes the blood test found; specificity is the share of normal results it correctly called normal.
| Study | Who took part | What it found |
|---|---|---|
| Pauta et al., 2025 (review of 8 studies) | 552 miscarriages | Sensitivity 78%, specificity 91%; no result in about 4 in 100, varying widely between studies |
| Copenhagen Pregnancy Loss Study, Lancet 2023 | 1,000 women, Denmark (accuracy checked against tissue in the first 333) | Sensitivity 85%, specificity 93%; about 11 in 100 inconclusive |
| Yaron et al., Human Reproduction 2020 | 86 losses before 14 weeks, Barcelona | Sensitivity 82% with settings adjusted for pregnancy loss, 55% with standard NIPT settings |
| Colley et al., Journal of Clinical Medicine 2020 | 57 miscarriages, Birmingham | Found 16 of the 27 chromosome changes seen in tissue (59%) |
The counting methods used in these studies cannot detect triploidy, so some studies, including the 2025 review and the UK study, left triploid pregnancies out of their accuracy figures.
In the 2025 review, a normal blood result lowered the chance of a chromosome change from about 61 in 100 to about 28 in 100, so it does not rule one out. An abnormal result is strongly suggestive but not definitive; where tissue is available, testing it can confirm or add detail.
Limitations
What the blood test cannot tell you
Even when the sample is taken at the right time, the test has blind spots, and it sometimes gives no result because there is too little placental DNA.
An extra whole set of chromosomes
Counting-based tests compare chromosomes with one another, so a pregnancy with three complete sets (triploidy) usually goes unseen. Depending on the study, extra whole sets account for roughly 1 in 10 to 1 in 5 of the chromosome changes found in miscarriage tissue.
Small or balanced changes
Missing or extra pieces of chromosome below the test's resolution, rearrangements where nothing is missing or extra, both copies of a chromosome coming from one parent (uniparental disomy) and single-gene conditions are not detected.
Placenta and embryo can differ
The test reads placental DNA. Occasionally the placenta carries a chromosome change the embryo does not, or the other way round (placental mosaicism), so the blood result can point the wrong way.
Your own DNA can show up
Rarely, a result reflects the mother's own DNA, such as a small chromosome variation she carries or, very rarely, an undiagnosed cancer. A vanished twin can have a similar effect. Unexpected results need review by a genetics specialist.
If you are leaning towards testing
A few practical points that can make things easier, whichever route you take.
Tell your early pregnancy unit you are thinking about genetic testing before a date is set for tablets or surgery.
Check who will do the scan before the sample, and that it will be close to the time the blood is taken.
If you are offered a private blood test, ask whether the laboratory's method has been checked specifically in pregnancy loss, and what it cannot detect.
If you are having surgery, ask whether some of the tissue can be sent fresh, without preservative, for genetic testing.
If you are waiting at home, ask your unit how to collect and store any tissue you pass, in case you want it tested.
Decide whether you want to know the pregnancy's chromosomal sex, as some reports include it, and who will go through the result with you.
If you would like to talk the timing through before deciding, book an online appointment with one of our genetic counsellors or call us on 020 3687 2939.
Getting help
Who to talk to about arranging a test
Your NHS early pregnancy unit remains the place for diagnosis, treatment and aftercare. A blood test for chromosome changes after miscarriage is not currently part of routine NHS care, and UK research, including a study funded by Tommy's, is still evaluating it. NHS genetic testing after miscarriage uses the pregnancy tissue instead.
Outside the NHS, blood-based testing after a miscarriage may be available privately. If you take that route, have the result explained by someone with genetics training, and make sure the tissue can still be tested if that is part of your plan.
We can help you think it through. Our genetic counsellors can go through, by video, whether testing is still possible for you and how the timing could work around your treatment, and our fetal medicine doctors can scan you if you want a second opinion on the diagnosis. Tissue testing is not booked online; it starts with a counselling appointment. The options are set out under how we can help.
For emotional support at any stage, Miscarriage UK runs a helpline on 0303 003 6464, and the pregnancy charity Tommy's can be reached on 0800 0147 800.
How we can help
Appointments that can help while the window is open
You can talk to one of our genetic counsellors online or be scanned at our City or West London clinic, alongside the care your NHS early pregnancy unit provides. No referral is needed. London Miscarriage Clinic is part of London Pregnancy Clinic, so booking opens on the London Pregnancy Clinic website. If timing is tight, call us or message us on WhatsApp.
Online, 30 minutes
Genetic counselling
A video consultation with a registered genetic counsellor, ideally before a date is set for tablets or surgery. Together you work out whether a blood test or tissue testing is realistic at this stage, what each could and could not tell you, and how to fit it around treatment. No test is arranged unless you want one. For a longer history, choose the 60-minute appointment.
From around 10 weeks
Second-opinion scan
If you are not yet sure the diagnosis is right, Dr Fred Ushakov can carry out a fresh, independent scan at our City clinic and talk you through what he sees before you decide on treatment or testing. Your early pregnancy unit continues to plan your care.
6–9 weeks
Repeat early scan
A scan with one of our fetal medicine doctors or specialist sonographers, for example when a repeat scan is due before a miscarriage can be confirmed, or to see whether the pregnancy is still in the womb before a blood sample. It is booked as our viability scan, at either clinic, and you receive a written report afterwards.
Questions about testing before the miscarriage completes
How soon after the diagnosis can the blood sample be taken?
Once the miscarriage has been confirmed and you have decided you want the test. As the tissue could start to come away at any time, it usually makes sense not to leave it long. While the diagnosis is still uncertain the test is not appropriate; see no heartbeat on scan for when a repeat scan or second opinion is needed.
I have already taken the first tablet. Is it too late?
Not necessarily, but the evidence is thin. The studies have focused on whether pregnancy tissue is still in the womb when the blood is taken, and there is little published information on whether the first tablet on its own changes the result. If you have started the tablets but have not passed the pregnancy, contact the team looking after you before doing anything else, and do not delay or skip a tablet to fit in a test without their advice.
Can I have the blood test and tissue testing as well?
Yes. A blood sample taken before treatment does not stop the tissue being tested later. Tissue testing can confirm a blood result or, depending on the method, pick up changes the blood test usually misses, such as triploidy. Our page on blood and tissue testing compared sets out the differences.
Is the blood test suitable after any kind of pregnancy loss?
No. The studies only included pregnancies a scan had confirmed to be inside the womb, and left out ectopic, unknown-location and molar pregnancies. Pregnancies with an empty sac (anembryonic pregnancy) were included in the largest study. Most of the research has involved losses in the first trimester.
Will the result change how my miscarriage is treated?
Usually not. The choice between waiting, tablets and surgery depends on your health, your preferences and clinical advice. The result is mainly about understanding why the loss happened and planning ahead: a chromosome change in the pregnancy is linked with a better outlook next time than a loss with normal chromosomes, and can help decide whether further investigations are worthwhile.
Do I need a referral to talk to you before my treatment?
No. You can book an online genetic counselling appointment or a scan with us directly, or call us on 020 3687 2939. It helps to keep your early pregnancy unit informed of any plans, as they will usually be managing your treatment and aftercare.
What if I would rather not know?
That is a completely valid choice, and many people decide against testing. Some find an explanation eases self-blame; others prefer not to add anything at an already difficult time. Talking it over with one of our genetic counsellors can help if you are torn, with no obligation to have a test. You may also find why did I miscarry? useful.
About this information
This page explains the general principles of testing before a miscarriage completes. It cannot take the place of advice from the professionals who know your situation, and reading it does not mean a particular test is right for you. If you are bleeding heavily, have severe pain or a fever, or feel faint or unwell, contact your early pregnancy unit or call 111 straight away. In an emergency, call 999.
Contact
Want to talk the timing through with us?
Sources & clinical references
The figures and clinical statements on this page are drawn from the sources below. Guidance evolves — always discuss your individual circumstances with a clinician.
- Human Reproduction (El Sammaa-Aru et al.)How big is the time window for cell-free fetal DNA testing after pregnancy loss and which factors are associated with a successful result?2026
- The Lancet (Schlaikjaer Hartwig et al.)Cell-free fetal DNA for genetic evaluation in Copenhagen Pregnancy Loss Study (COPL): a prospective cohort study2023
- Prenatal Diagnosis (Pauta et al.)Genome-wide cell-free DNA analysis for aneuploidy detection in miscarriages: test performance meta-analysis2025
- Human Reproduction (Yaron et al.)Maternal plasma genome-wide cell-free DNA can detect fetal aneuploidy in early and recurrent pregnancy loss2020
- Journal of Clinical Medicine (Colley et al.)Cell-free DNA in the investigation of miscarriage2020
- NICEEctopic pregnancy and miscarriage: diagnosis and initial management (NG126)2026
- BMJ (Luise et al.)Outcome of expectant management of spontaneous first trimester miscarriage: observational study2002
- RCOGRecurrent Miscarriage (Green-top Guideline No. 17)2023
- NHS EnglandNational Genomic Test Directory: testing criteria for rare and inherited disease, v9.12026
- North West Genomic Laboratory HubAcceptance criteria and requirements for solid tissue samples following loss of pregnancy2025
- Tommy'sUsing fetal DNA to detect chromosomal abnormalities following miscarriageAccessed October 2026
- NHSMiscarriage2026