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Blood Test or Pregnancy Tissue Test: Which Is Possible for Me?

Which genetic test is possible after a miscarriage depends mostly on where the pregnancy is now. While it is still in the womb, a blood test may be possible. Once it has passed and tissue was kept, the tissue itself may be tested. If neither applies, your history and earlier results guide the next step.

Of the two, testing the tissue gives the more definitive answer. A blood test is newer and less accurate, but it can be done before tablets or surgery. Our genetic counsellors can help you work out quickly which route is still open to you.

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The basics

Two routes to the same question

Both tests try to answer one question: were this pregnancy's chromosomes affected, for example by an extra or a missing chromosome? About half of early miscarriages happen for this reason, usually by chance.

A blood test, often called a cell-free DNA (cfDNA) test, uses a sample of your blood. While pregnancy tissue is still in the womb, the placenta sheds fragments of its DNA into your bloodstream, and the laboratory counts them chromosome by chromosome. After a miscarriage, typically only around 5 in 100 of these fragments are placental; the rest are yours.

A tissue test examines the pregnancy tissue itself, once it has passed or been removed, usually with a chromosomal microarray that checks DNA across every chromosome. Because it looks at the pregnancy directly, research uses it as the yardstick for judging blood tests, although it can fail too.

Put simply, the blood test pieces together a letter from scraps mixed into a large pile of your own paperwork. The tissue test reads the letter itself.

A genetics laboratory with DNA analysis instruments on the benches and a scientist in a white coat working at computer screens
Both kinds of sample are analysed in a specialist genetics laboratory

Where are you now?

Which test may still be possible: three situations

Find the situation closest to yours. If you are not sure whether tissue is still in your womb, a scan can show this.

01

The pregnancy is still in your womb

A miscarriage has been confirmed on a scan but has not passed yet. Both routes may be open: a blood sample before anything is done, then tissue testing afterwards if tissue can be collected.

Placental DNA in your blood is highest while the tissue is in place, so the sample is best taken before tablets or surgery, after a scan that confirms tissue remains and checks for a twin or 'vanished twin'. Blood testing has not been studied when the location of the pregnancy is uncertain or a molar pregnancy is suspected; both need their own medical care first, so it is not usually suitable then. If you doubt the diagnosis itself, a second-opinion scan comes first.

02

The pregnancy has passed and tissue was collected

If tissue was collected at surgery, or kept after a miscarriage at home or in hospital, testing it is usually the better route: a microarray gives a result in over 9 in 10 suitable samples. The tissue must reach the laboratory fresh and without preservative, because UK genetics laboratories generally do not accept tissue that has been put in formalin.

A blood test is much less useful now. In a large Danish study, about 9 in 100 blood tests gave no result while tissue was still in the womb, rising to about 27 in 100 when the sample was taken 12 to 24 hours after it had passed.

03

The pregnancy has passed and there is no tissue to test

This is common: in the same Danish research, about a third of women either could not collect tissue or collected a sample that was likely to be their own tissue rather than the pregnancy's. What comes next depends on your history and on any earlier results.

After a first or second miscarriage with no other concerns, there is usually no genetic test left for this pregnancy; the most useful step is often knowing how tissue could be tested if this ever happened again.

After three or more miscarriages with no tissue tested, or if an earlier miscarriage showed an unbalanced rearrangement, a chromosome test for both parents may be offered. A family history of chromosome rearrangements is also worth raising with a genetics specialist.

Side by side

Blood test and tissue test compared

The main differences at a glance. Figures describe groups of people, not any one pregnancy.

What differsBlood test (cell-free DNA)Tissue test (microarray)
When it can be doneAfter a miscarriage is confirmed, while tissue is still in the womb; ideally before tablets or surgeryOnce the tissue has come away or been removed, provided it was kept fresh and unpreserved
The sampleYour blood, which carries a small share of placental DNAThe pregnancy tissue, sometimes with a sample of your blood for comparison
What it checksWhole extra or missing chromosomes, and sometimes larger missing or extra piecesExtra or missing chromosomes and smaller missing or extra pieces; a SNP array can also pick up triploidy
What it may missTriploidy (with most methods), small changes, mosaicism, balanced rearrangements and single-gene conditionsBalanced rearrangements, single-gene conditions, low-level mosaicism and very small changes; arrays without SNPs may miss triploidy
AccuracyFound about 78 in 100 of the changes seen in tissue (8 studies pooled, triploidy left out); a screening-type resultUsed in research as the reference for judging blood tests, although it can also fail or test your cells by mistake
Why there may be no resultNot enough placental DNA, especially after tissue has passed: about 4 in 100 tests pooled, 11 in 100 in the largest studyNo tissue collected, tissue put in formalin, or only your own tissue in the sample; karyotyping also fails in about 1 in 5 when cells do not grow
Your own DNAMost of the DNA in the sample is yours, so a variation of your own can occasionally misleadYour cells can be mixed with the tissue; SNP arrays or a sample of your blood can check for this
PracticalitiesOne blood sample, ideally just after a scan; not part of standard NHS careCollected and sent without preservative; on the NHS, usually from the third miscarriage, and UK guidance also advises it after any loss from 14 weeks

Accuracy

Which result can you rely on more?

Testing the tissue gives the more definitive answer, and we would rather say so plainly. A blood result is a useful pointer rather than a final answer, but when no tissue can be collected it may be the only information you can get.

Pooling 8 studies of 552 miscarriages, a 2025 analysis found the blood test detected about 78 in 100 of the chromosome changes identified in tissue (leaving out triploidy, which these tests cannot see), and gave a correct normal result in about 91 in 100 pregnancies with normal chromosomes.

The largest study recruited 1,000 women in Denmark and checked accuracy against tissue in the first 333, finding figures of 85 in 100 and 93 in 100 on those same two measures; about 1 in 9 of all its tests were inconclusive. A smaller UK study from Tommy's found the test correctly identified about 6 in 10 changes.

What about a single result? Using the pooled figures, where about 6 in 10 miscarriages had a chromosome change, an abnormal blood result would be right about 93 times in 100. A normal result is less reassuring: around 28 in 100 such pregnancies would still have a chromosome change, so it does not rule out a chromosomal cause. These figures shift with age and history, because they depend on how common chromosome changes are in the group being tested.

A shared complication

Your own DNA can affect both tests, in different ways

Your own DNA is part of the picture with either test, which is one reason results need expert interpretation.

Blood

In a blood test

Most of the DNA in your blood is yours. Occasionally a result reflects you rather than the pregnancy: a small chromosome variation you have always had, a low-level mix of cells with one X chromosome (more common with age) or, very rarely, an undiagnosed cancer. A vanished twin can have the same effect.

Tissue

In a tissue test

Pregnancy tissue is often mixed with your own. With traditional karyotyping your cells can outgrow the pregnancy's, so a 'normal female' (46,XX) result may describe you. SNP arrays, or a sample of your blood, can check for this. If the sample is entirely your own tissue, there is no result.

Not either-or

Using both tests together

If the pregnancy is still in your womb, you need not choose. A blood sample can be taken before treatment and the tissue tested afterwards if it is collected, so each acts as a check on the other. In one US study, the blood test identified a trisomy in a pregnancy whose tissue gave no result because the sample contained only the mother's cells.

Whether both are worthwhile depends on your history and on how you would use the answer. It is a good question to bring to a genetic counselling appointment.

NHS care

Testing on the NHS: who is offered what

Your NHS early pregnancy unit confirms and manages a miscarriage free of charge and should stay at the centre of your care. NHS genetic testing uses pregnancy tissue, not a blood test, and is offered in particular circumstances.

Tissue testingNHS criteria cover three or more miscarriages, and UK guidance (RCOG) also advises it after any miscarriage from 14 weeks. It uses a quick test for the commonest changes plus a microarray.
Earlier testingafter a single miscarriage with features that suggest a chromosome condition.
Parents' chromosomesafter an unbalanced tissue result, or in some cases after three or more miscarriages where no tissue could be tested. NHS guidance notes that testing any future pregnancy loss is usually more informative.

Blood-based testing after miscarriage is not part of standard NHS care, and UK research, including studies funded by Tommy's, is still evaluating it. If you have had one or two miscarriages, or would like testing that is not offered locally, private testing may be possible; a genetic counsellor can explain what is currently available and how reliable it is.

Before you contact us

What helps us advise you quickly

Time can be short, so it helps to have these details ready when you call or book. Do not worry if you cannot find them all.

The date and findings of the scan that confirmed the miscarriage

Your management plan (waiting, tablets or surgery) and the date of any treatment

Whether bleeding has started, or tissue may already have passed

Whether an earlier scan in this pregnancy showed twins

Any previous miscarriages, and genetic results for you, your partner or an earlier pregnancy

How we can help

Support from our genetics team

Our clinics are in the City of London and West London. Genetic counselling is by video, so you do not need to live nearby to speak to us.

Arranged through counselling

Pregnancy tissue testing

Chromosome testing of pregnancy tissue, arranged through accredited laboratory partners, with counselling before and after. Contact us before treatment if you can.

Learn more

Only when indicated

Parental karyotype

A blood test of one or both partners' chromosomes via Jeen Health, when a tissue result or your history points to it: £290 for one person or £550 for a couple.

Learn more

Blood test or tissue test: your questions

Could a standard pregnancy NIPT be used instead?

Not reliably. It uses the same principle, but in a harder setting. After a miscarriage there is usually much less placental DNA in your blood. In an Israeli and Spanish study, standard prenatal settings detected about 55 in 100 chromosome changes, against about 82 in 100 with thresholds designed for pregnancy loss. The test also needs to cover every chromosome, not only the few that some prenatal tests focus on.

If the blood test finds no change, can I be sure there wasn't one?

No. A normal blood result makes a chromosomal cause less likely but cannot rule it out, and most blood tests cannot see triploidy at all. If tissue becomes available, testing it gives a firmer answer.

Is this blood test the same as a chromosome test for parents?

No. The blood test after miscarriage reads placental DNA to learn about the pregnancy. A parental karyotype examines your own and your partner's chromosomes for a balanced rearrangement. Neither the blood test nor a tissue microarray can see a balanced rearrangement, because nothing is missing or extra; finding an unbalanced one in the tissue is usually what prompts parental testing.

The pregnancy passed yesterday. Is a blood test still worth having?

Usually the tissue, if any was kept, is the better focus. Placental DNA can still be measured for up to about 3 days after the tissue has come away or been removed, but it falls markedly after about 12 hours, and around 3 in 10 samples gave no result by day 3 in the Danish study. Call us on 020 3687 2939 to talk it through.

I miscarried at home and kept the tissue. Can it be tested?

Possibly. Keep it in a clean container without any preservative, and contact your early pregnancy unit, or us, promptly for advice on getting it to a laboratory. The laboratory checks whether pregnancy tissue is present and may ask for a sample of your blood. If the sample is only your own tissue, there is no result.

I am having surgery. How do I make sure the tissue can be tested?

Ask the team beforehand to send some tissue fresh to a genetics laboratory, rather than putting it all in formalin: in the UK, NHS genetics laboratories treat formalin-preserved samples as unsuitable for this testing.

About this information

This page compares two kinds of genetic testing in general terms and cannot tell you which is right for you; that needs a clinician who knows your history and scan findings. If you have heavy bleeding, severe pain, a fever or feel faint, contact your early pregnancy unit or NHS 111 straight away, or call 999 in an emergency.

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Not for emergencies. If you have heavy bleeding or severe pain, call 999 or go to A&E.

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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.

  1. Prenatal Diagnosis (Pauta et al.)Genome-wide cell-free DNA analysis for aneuploidy detection in miscarriages: test performance meta-analysis2025
  2. The Lancet (Schlaikjaer Hartwig et al.)Cell-free fetal DNA for genetic evaluation in Copenhagen Pregnancy Loss Study (COPL): a prospective cohort study2023
  3. 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
  4. Human Reproduction (Yaron et al.)Maternal plasma genome-wide cell-free DNA can detect fetal aneuploidy in early and recurrent pregnancy loss and can be used to direct further workup2020
  5. Journal of Clinical Medicine (Colley et al.)Cell-free DNA in the investigation of miscarriage2020
  6. Journal of Clinical Medicine (Kutteh et al.)Cell-free DNA analysis of fetal aneuploidies in early pregnancy loss2024
  7. Genetics in Medicine (Sahoo et al.)Comprehensive genetic analysis of pregnancy loss by chromosomal microarrays: outcomes, benefits, and challenges2017
  8. The Application of Clinical Genetics (Papas & Kutteh)Genetic testing for aneuploidy in patients who have had multiple miscarriages: a review of current literature2021
  9. RCOGRecurrent Miscarriage (Green-top Guideline No. 17)2023
  10. NHS EnglandNational Genomic Test Directory: testing criteria for rare and inherited disease (version 9.1)2026
  11. North West Genomic Laboratory Hub (Manchester University NHS Foundation Trust)Acceptance criteria, requirements for cytogenetic analysis, and tissue disposal policy for solid tissue samples following loss or termination of pregnancy2025
  12. Tommy'sUsing fetal DNA to detect chromosomal abnormalities following miscarriageAccessed October 2026