Reading a Miscarriage Genetic Test Report: What Each Result Means

Results from miscarriage genetic testing often arrive in shorthand, such as 47,XX,+16 or 'no abnormality detected'. On this page we translate each common result, say whether it tends to come back in a later pregnancy and set out what usually comes next.

Most chromosome changes found after a miscarriage are one-off chance events: nothing either of you did brought them about, and only rarely do they mean a parent's own chromosomes are different. Our genetic counsellors can go through your own report with you.

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Before you open the report

A genetic result can arrive weeks after the miscarriage, just as life was starting to settle, and it can bring relief, sadness or frustration whatever it says. The team who arranged the test should talk it through with you, and our genetic counsellors are here if you want longer to go through it; you do not have to decode it alone.

Hold on to one fact while you read. Roughly 1 in 2 early miscarriages are the result of a chromosome change in the pregnancy, and in nearly all of them the parents' own chromosomes are typical. In one hospital series of over 1,200 miscarriages, only about 1 or 2 in every 100 abnormal results were an unbalanced rearrangement passed on from a parent.

A dark-haired woman in a soft cream sweater sits in a pale chair, hands resting in her lap, looking calm — Most chromosome findings record a single chance event, not a pattern that will repeat

Decoding the shorthand

A karyotype gives the number of chromosomes first, then the sex chromosomes, then any change. So 46,XY is a typical male result, 47,XX,+16 is a female pregnancy with an extra chromosome 16, 45,X has a single sex chromosome and 69,XXY is triploidy.

Codes for structural changes include del (deletion), dup (duplication), t (translocation) and der (a rearranged chromosome), sometimes followed by dn (arose for the first time) or by mat, pat, dmat or dpat (passed on from the mother or father). Microarray reports start with arr and end each finding with a copy number: x2 is usual, x1 means a copy is missing and x3 means there is an extra one.

Ten results at a glance

Find the line closest to your report, then read the detail below. The middle column gives the usual picture; your age, history and exact finding can change it.

Result on the report	Likely to happen again?	Parents' chromosomes tested?
Trisomy (for example 47,XX,+16)	Usually a one-off	Not usually
Monosomy X (45,X)	Usually a one-off	Not usually
Triploidy (69 chromosomes)	Usually a one-off; if it was molar, about 1 in 100 go on to have another molar pregnancy	Not usually
Deletion	Depends on whether it was inherited	Sometimes
Duplication	Depends on whether it was inherited	Sometimes
Copy number variant of uncertain significance	Cannot be judged from this finding alone	Only if it would help interpret it
Unbalanced rearrangement	Depends on the parents' results	Yes, usually offered
No abnormality detected	Cannot be judged from this result; after repeated losses, other causes are checked	Not usually
Normal female (46,XX)	Unclear until contamination is ruled out	Depends on whether the result is reliable
Failed test or no-call	Unknown	Sometimes, depending on your history

How often each type of result turns up

Figures from UK guidance and large laboratory series. They describe groups of pregnancies, not what happened in any single one.

About 1 in 2 early miscarriages stem from a chromosome change in the pregnancy

52 to 63 in 100 abnormal results are a trisomy, the commonest finding

11 to 15 in 100 abnormal results are a missing chromosome, mostly monosomy X (45,X)

10 to 19 in 100 abnormal results have one or more whole extra sets of chromosomes

6 to 7 in 100 abnormal results are structural: missing, extra or rearranged pieces

When a whole chromosome, or a whole set, is extra or missing

These three findings make up most abnormal results after an early miscarriage. Each comes from chromosomes being shared out unevenly as an egg or sperm forms, at fertilisation or in the first cell divisions.

Trisomy: three copies of one chromosome

There were 47 chromosomes in the pregnancy rather than the usual 46. Most trisomies start with an error as the egg matures, so they become more frequent as the egg-provider gets older; with donor eggs, the donor's age is what counts.

A trisomy is usually a one-off, and pregnancies after one generally fare better than pregnancies after a chromosomally normal loss. Parents are not usually tested unless the report or family history hints at an inherited rearrangement.

Data from North America suggest that, after a trisomy miscarriage, a later pregnancy is a little under twice as likely as expected for the mother's age to have a trisomy such as Down's syndrome. For most people the overall chance is still low, and there are screening options next time.

Monosomy X (45,X): one sex chromosome instead of two

The pregnancy had a lone X chromosome, with no partner X or Y. It often arises when the sex chromosome from the sperm is lost and, unlike a trisomy, it does not become more common with the mother's age. It is regarded as chance and is not, on its own, a reason to test the parents.

If 45,X came from a blood test, a genetics specialist should review it, because the signal may arise in the placenta only, or in a small share of the mother's own cells.

Triploidy: a whole extra set

The pregnancy had 69 chromosomes, three full sets instead of two. It happens by chance, does not seem to be linked to the mother's age and is usually a one-off. Blood tests that count DNA fragments cannot detect it.

When the extra set is paternal, usually because two sperm entered one egg, it may have been a partial molar pregnancy; hCG hormone levels are then checked, with a specialist centre, until two normal results a month apart. A maternal extra set is not molar. Molar pregnancy comes back in about 1 in 100 people who have had one, and the risk is smaller after a partial mole than after a complete mole. If your report does not say where the extra set came from, ask whether follow-up is needed.

When part of a chromosome is missing, doubled or rearranged

Structural findings are less common, but a chromosomal microarray picks up smaller changes than older methods. The key question is whether the change arose for the first time in that pregnancy or was passed on.

A deletion or a duplication

In a deletion, part of a chromosome has been lost; in a duplication, part of one appears twice. Some are large enough to explain a miscarriage, while others turn out to be of no medical importance. Many arise for the first time and are then treated as one-off events, but because one can be half of an unbalanced rearrangement, a genetics team may suggest checking both parents.

A copy number variant of uncertain significance

This is a small extra or missing section that has not been clearly linked with any health effect, often shortened to VUS. In one large study of missed miscarriages, about 4 or 5 in every 100 samples had one. It should not be taken as the cause unless a genetics professional says so, and they can advise whether testing the parents would help clarify it.

An unbalanced rearrangement

Pieces of two chromosomes have changed places, leaving too much of one and too little of another. In two hospital studies, between about 3 and 7 in 10 had been inherited from a parent who carries a balanced form, with nothing missing or extra; the rest arose for the first time in that pregnancy. UK guidance recommends offering both parents a karyotype, and a carrier would be referred to a genetics team.

Carriers are healthy and the outlook is good. A large study from the Netherlands of couples with two or more miscarriages found that, over about six years, 83 in 100 carrier couples had a healthy child, against 84 in 100 couples without a rearrangement, though carriers were more likely to miscarry again along the way.

For a carrier couple, the chance that a pregnancy with an unbalanced form survives into the second trimester is low, below 1 in 100. Choices such as prenatal testing or IVF with embryo testing (PGT-SR) are covered in parental chromosome testing.

When the result is normal, 'female' or missing

These can be the hardest results to accept, because they give no clear reason.

No chromosome cause seen

No abnormality detected

Nothing extra or missing was found at the level the test can see; some tests check only a few chromosomes, so ask which was used. It does not rule everything out: single-gene changes are too small for these tests, and maternal factors like antiphospholipid syndrome, thyroid disease or an unusually shaped womb can play a part. A normal result is linked with a higher chance of another loss than a chromosomal one, so after repeated losses ask about recurrent miscarriage checks.

Check for contamination

Normal female (46,XX)

The mother's cells are female and often mixed in with pregnancy tissue. With traditional karyotyping, one study found contamination with her cells in around 1 in 5 samples, which can give a 46,XX result that describes her, not the pregnancy. A SNP microarray or a comparison with her blood can tell the two apart, and NHS testing criteria treat a sample that proves to be maternal as a failed test. A 46,XY result cannot come from the mother.

No answer either way

Failed test or no-call

Tissue tests fail when the sample holds no pregnancy tissue or was put in formalin, or, with karyotyping, when the cells do not grow (about 1 in 5 attempts). Blood tests give a no-call when there is too little placental DNA: about 4 in 100 on average across studies, but over 1 in 4 in one early study. A failed result is neither normal nor abnormal. Ask whether any tissue was frozen and could be tried another way.

Results that came from a blood sample

A blood test taken after a miscarriage is diagnosed reads placental DNA in the mother's bloodstream rather than the pregnancy tissue, so it behaves more like a screening test than a diagnosis. More in how the blood test works.

A 2025 review pooled eight studies that compared the blood test with tissue results. It picked up about 78 in 100 of the chromosome changes found in tissue, and about 9 in 100 losses with normal tissue were wrongly flagged. About 6 in 10 losses had a chromosome change, and at that rate an abnormal blood result was confirmed about 93 times in 100. When it reported none, about 28 in 100 still had one.

So an abnormal blood result is fairly dependable, but a normal one is much less so, and triploidy was left out of those figures because the test cannot detect it. Counting-based blood tests also cannot see balanced rearrangements or deletions and duplications below their resolution, and may miss changes present in only some cells. Very occasionally a result reflects the mother's own DNA, a placenta-only change or a vanished twin. Any puzzling result should go to a genetics specialist.

Should your own chromosomes be checked?

Testing the parents looks for a balanced rearrangement: all the genetic material is present but arranged differently. Carriers are usually healthy and unaware of it.

Usually offered

After a tissue result showing an unbalanced rearrangement, UK guidance says both parents should be offered a karyotype. If one of you is a carrier, relatives can be offered testing too.

Sometimes offered

If no tissue could be tested, because none was collected or the test failed, the RCOG advises offering it. NHS criteria are narrower (three or more losses with failed testing and none tested before, or five or more untested) and note that testing a future loss usually tells you more.

Not usually needed

A trisomy, 45,X, triploidy or normal result does not usually point to a parent's rearrangement. European guidance notes that carriers are rarely found when the woman is 39 or older, there have been fewer than three losses and nothing relevant runs in the family.

When a genetics professional helps most

European guidance on recurrent pregnancy loss says every couple with an abnormal chromosome result, from pregnancy tissue or from the parents, should receive genetic counselling. It is particularly worth asking for when:

The result is an unbalanced rearrangement, or one of you carries a balanced one
The report mentions a deletion, a duplication or a variant of uncertain significance
The result was triploidy and it is unclear whether the pregnancy was molar
A blood result conflicts with a scan or tissue result, or hints at something in your own DNA
You are planning another pregnancy and weighing up screening or diagnostic tests

Getting your own result explained

On the NHS, the report goes to whoever requested the test, usually the early pregnancy unit, gynaecology team or recurrent miscarriage clinic. They can explain it and refer you to a regional clinical genetics service if the result suggests something could be inherited.

If you need to talk, Tommy's midwife-led line is free on 0800 0147 800, and Miscarriage UK can be phoned on 0303 003 6464; both are there for anyone affected by miscarriage.

If you would like a private appointment, or more time with your report than a busy clinic can give, you can book one with our team directly. The options, from a 30-minute video appointment with a genetic counsellor to a review by our consultant in clinical genetics, are set out below.

How we can help

Help with your result at London Miscarriage Clinic

You can have a report explained by video, or arrange the follow-up it points to, alongside any NHS care you are receiving. No referral is needed. London Miscarriage Clinic is part of London Pregnancy Clinic, so booking opens on the London Pregnancy Clinic website.

Online, 30 minutes

Genetic counselling

A video appointment with one of our registered genetic counsellors, a team led by Ailidh Watson. Have your report to hand and we go through it with you: what the finding means, whether it is likely to be a one-off, whether testing either parent would add anything and what it could mean next time. A 60-minute appointment allows more time for a complex history.

Learn more Book £80

Doctor-led, by enquiry

Clinical genetics consultation

For findings that need a medical view, such as a rearrangement that may run in the family, a mosaic or uncertain result, or a blood result that hints at something in your own DNA. Dr Harry Leitch, Consultant in Clinical Genetics, reviews your reports and family history and advises on next steps, including whether further testing is likely to be informative. Appointments last 30 to 90 minutes.

Learn more

Only when indicated

Parents' chromosome test (karyotype)

A blood test that checks one or both parents for a balanced rearrangement. It is most useful after a tissue result showing an unbalanced rearrangement, or when tissue from repeated losses could not be tested, so we usually suggest genetic counselling first. Results typically take two to three weeks. Testing a couple costs £550.

Learn more Book £290

After repeated losses

Recurrent miscarriage package

If you have had repeated losses, especially with normal chromosome results, the wider checks matter. The package is a consultation and pelvic scan with a consultant gynaecologist at our City clinic, with blood tests that include checks for antiphospholipid syndrome and thyroid function. You book with a £300 deposit, which comes off the package price.

Learn more Book £980

Questions about genetic results

We are both healthy. How could the pregnancy have had a chromosome problem?

Most chromosome changes arise during the making of an egg or sperm, or in the first cell divisions after fertilisation. They are copying errors in that one pregnancy, not a sign of anything wrong with your own chromosomes or health.

The report says 'mosaic'. What does that mean?

The laboratory found a mixture of cells, some with a chromosome change and some without. After a miscarriage this can reflect a change limited to the placenta rather than the embryo. Mosaic findings are harder to interpret, so they are worth going through with a genetics professional.

One miscarriage had a chromosomal cause. Do I still need other tests?

One result explains one pregnancy. After several losses, different pregnancies can end for different reasons, so tests for antiphospholipid syndrome and thyroid disease, and a scan of the womb's shape, may still be suggested. Where one partner is a carrier of a balanced rearrangement, only about a third of the couple's losses are due to it.

The blood test and the tissue test disagree. Which should I go by?

Tissue testing is the standard that blood tests are measured against, so a reliable tissue result usually carries more weight. Differences can arise because placental DNA is not always the same as the embryo's, or because a 46,XX tissue result was really the mother's cells. A genetics specialist can compare both reports.

All the chromosome results were normal. Can anything else be tested?

Research has linked a share of miscarriages to variants in single genes, or to changes below the resolution of chromosome tests, but looking for these is not part of routine NHS care. After repeated losses, the more useful step is usually making sure the standard recurrent miscarriage investigations have been done.

Can I book an appointment about my result without a referral?

Yes. You can book an online genetic counselling appointment yourself, without a letter from your GP or hospital, and because it takes place by video you can join from home. It helps to have your laboratory report with you.

If your test was arranged on the NHS, the team who requested it, and the regional clinical genetics service they can refer you to, remain free routes for explaining it.

About this information

This page explains genetic results in general terms only. It cannot interpret your own report, and it is no substitute for advice from the team looking after you or a personal appointment. If bleeding becomes heavy, pain turns severe, a fever starts or you feel faint, make your early pregnancy unit or 111 your first call, and 999 if it is an emergency.

Contact

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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.

RCOGRecurrent Miscarriage (Green-top Guideline No. 17)2023
ESHRERecurrent pregnancy loss guideline, 2022 update2023
NHS EnglandNational Genomic Test Directory: testing criteria for rare and inherited disease, version 9.12026
Scientific Reports (Xue et al.)Genetic analysis of chorionic villus tissues in early missed abortions2023
Molecular Cytogenetics (Wu et al.)Comprehensive analysis of early pregnancy loss based on cytogenetic findings from a tertiary referral center2021
Prenatal Diagnosis (Pauta et al.)Genome-wide cell-free DNA analysis for aneuploidy detection in miscarriages: test performance meta-analysis2025
BMJ Medicine (Joyce et al.)Advances in the diagnosis and early management of gestational trophoblastic disease2022
BMJ (Franssen et al.)Reproductive outcome after chromosome analysis in couples with two or more miscarriages: case-control study2006
American Journal of Human Genetics (Warburton et al.)Trisomy recurrence: a reconsideration based on North American data2004
Tommy'sRecurrent miscarriage2026
Miscarriage UKMiscarriage UK (The Miscarriage Association): information and support lineAccessed October 2026
Association for Diagnostics & Laboratory Medicine (Repnikova)Pearls of Laboratory Medicine: whole genome analysis using microarrays2015