What Does My Miscarriage Genetic Test Result Mean?

A genetic report after a miscarriage can read like code. This guide explains each common result, from trisomy and monosomy X to a variant of uncertain significance or a test that gave no answer, whether it is likely to happen again, and when testing both parents or genetic counselling helps.

Most chromosome changes found after miscarriage are one-off chance events from the moment the egg, sperm or first cells formed, not something either of you caused. If you have a report in front of you, our genetic counsellors can go through it with you by video.

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Before you read the report

Most results describe something that happened once, by chance. About 1 in 2 early miscarriages is caused by an extra, missing or rearranged chromosome in the pregnancy, and in most cases both parents' own chromosomes are normal (RCOG, 2023).

Check which test was used, because 'normal' means something different for each. A rapid test, usually QF-PCR, covers only chromosomes 13, 18 and 21 plus certain sex chromosome conditions (NHS England GeNotes). A microarray checks every chromosome, including small missing or extra pieces. Karyotyping grows cells and examines the chromosomes under a microscope. A blood-based test analyses placental DNA circulating in the mother's bloodstream and gives a screening-type answer.

Reports use shorthand: '46,XX' or '46,XY' means 46 chromosomes with female or male sex chromosomes, and '47,XX,+16' means an extra chromosome 16. Our genetic counsellors can take you through yours line by line.

Woman in a cream jumper seated in a pale armchair, looking calmly ahead — There is no right way to feel when a result arrives

Context

Why most results point to chance

These are averages from research studies and cannot predict what happens in an individual pregnancy; full references appear below.

1 in 2 Early miscarriages that result from a chromosome change in the pregnancy, usually when both parents' own chromosomes are normal (RCOG patient information, 2023)

Half to two-thirds Abnormal results that are a trisomy, usually a chance error as the egg matured (RCOG, 2023; Wu et al., 2021)

83 in 100 Couples with a balanced rearrangement, after two or more miscarriages, who had at least one healthy child at follow-up; for non-carrier couples the figure was 84 (Franssen et al., BMJ 2006)

In depth

Each result explained

Each card covers what a tissue result means, whether it is likely to recur and what usually happens next. Your own chances depend on your age, your history and the exact finding, so treat these as a starting point for a conversation.

Some reports describe a change as mosaic, meaning only some of the cells tested carry it. This made up about 1 in 20 abnormal results in one study (Wu et al., 2021), and its meaning needs interpreting by a genetics professional.

Trisomy: an extra copy of one chromosome

Three copies of one chromosome instead of two, so 47 in total. It is the commonest finding after miscarriage, about half to two-thirds of abnormal results, and trisomy 16 alone makes up about a quarter of trisomies (Xue et al., 2023).

It usually arises by chance as the egg matures, more often as the egg-provider gets older. It does not suggest a chromosome problem in either of you and, compared with a miscarriage that had normal chromosomes, it points to a more hopeful outlook for the next pregnancy. Age still counts, though: an older woman after a trisomy may still have lower chances than a younger woman after a loss with normal chromosomes (RCOG, 2023).

Monosomy X (45,X): a missing sex chromosome

A single X chromosome and no second X or Y. It is one of the most frequent findings, is no more frequent in older mothers, and often results from loss of the sex chromosome carried by the sperm (Xue et al., 2023). In an ongoing pregnancy the same pattern is called Turner syndrome; see sex chromosome conditions.

From a blood test, a monosomy X signal needs extra care: it can come from the placenta alone or from some of the mother's own cells.

Triploidy: a whole extra set of chromosomes

Three full sets of chromosomes, 69 instead of 46. With the rarer tetraploidy it makes up roughly 1 in 10 to 1 in 5 abnormal results (RCOG, 2023; Wu et al., 2021). It arises by chance around fertilisation. The extra set can come from the father, for example when two sperm fertilise one egg, or from the mother. It does not appear to be linked to the mother's age (Xue et al., 2023).

When the extra set comes from the father, the pregnancy may have been a partial molar pregnancy, which needs hCG follow-up through a specialist centre. A chromosome count alone cannot show which parent the extra set came from, so the tissue is also examined under a microscope and sometimes genotyped (Joyce et al., 2022).

Deletions and duplications: a missing or extra piece

A section of a chromosome is missing (a deletion) or doubled (a duplication). Large ones show on a karyotype; smaller ones, often called copy number variants or CNVs, only on a microarray or similar genome-wide test, which picks them up in roughly 5 to 7 in every 100 miscarriages beyond those older methods detect (RCOG, 2023).

Whether a change explains the loss depends on its size and the genes involved, and the report will say how significant the laboratory thinks it is. A missing end piece on one chromosome alongside an extra end piece of another can signal an unbalanced rearrangement, explained in card 06 (Xue et al., 2023).

A variant of uncertain significance

A piece of chromosome is missing or duplicated, but its effect is not yet known; this is often shortened to VUS. It may have nothing to do with the miscarriage. In one large series, 52 of the 77 small changes found by genome-wide testing fell into this group (Xue et al., 2023).

Keep the full report, as knowledge about individual variants grows. A genetic counsellor, or our consultant through a clinical genetics consultation, can explain what is known and whether testing a parent would help.

Unbalanced rearrangement: swapped or turned material

Chromosome pieces have swapped places (a translocation) or turned round (an inversion), leaving the pregnancy with some material missing and some extra. A parent carried a balanced form, with everything present but rearranged, in about 1 in 3 cases in one study (Wu et al., 2021) but about 7 in 10 in another (Xue et al., 2023). Otherwise the change arose new, by chance, so testing you both is the only way to know which applies.

Both partners should be offered a karyotype, and carriers referred to a genetics team (RCOG, 2023). Carriers are healthy. Among carrier couples in a Dutch study, 83 in 100 had at least one healthy child, against 84 in 100 non-carrier couples, although carriers miscarried more often (Franssen et al., 2006).

No abnormality detected

No chromosome change was seen at the level of detail the test can reach. That does not rule out other causes, either in the pregnancy, such as single-gene changes, or in the mother's health (ESHRE, 2022). If only a rapid test was done, most chromosomes were not checked.

Where losses keep happening, RCOG guidance advises checking for antiphospholipid syndrome, testing thyroid function and imaging the womb's shape, ideally with 3D ultrasound (RCOG, 2023); see recurrent miscarriage.

'Normal female' (46,XX): whose cells were tested?

This may be a female pregnancy with normal chromosomes, or the mother's own tissue, which is often mixed in with pregnancy tissue. Traditional karyotyping cannot tell these apart (ESHRE, 2022), and in one study contamination affected about 22 in 100 karyotyped samples (RCOG, 2023).

SNP microarrays, or comparison with the mother's blood, can check. If contamination was excluded, read the result as no abnormality detected; if not, it may describe the mother's cells rather than the pregnancy's, so treat it with caution.

No result, or a failed test

Karyotyping relies on cells growing in the laboratory, which fails in roughly 1 in 5 samples (RCOG, 2023), whereas microarray does not need living cells. A sample can also prove to be entirely the mother's tissue, or be unsuitable because it was placed in formalin, the preservative used for routine pathology. A blood-based test fails when too little placental DNA is present.

A failed test is not an abnormal result and says nothing about the cause. It is worth asking whether any tissue is still stored and could be tested another way. Parents may be offered karyotypes in some situations, but testing any future loss is usually the most informative step (NHS England GeNotes).

Blood-based testing

If your result came from a blood test

A blood-based (cell-free DNA) test reads fragments of placental DNA in the mother's blood. The placenta's chromosomes usually, but not always, match the pregnancy's, so these are screening-type results. Pooled figures from eight studies, in which about 6 in 10 miscarriages had a chromosome change, help put them in context (Pauta et al., 2025); our genetic blood test guide explains how the test works.

A chromosome change was reported

On the pooled figures, a positive result means roughly a 93 in 100 chance that tissue testing would also show a chromosome change. A mismatch can come from a change confined to the placenta, a vanished twin or the mother's own DNA, so unexpected findings deserve a genetics review.

No chromosome change was found

Less conclusive: a negative result still leaves an estimated 28 in 100 chance of a chromosome change in the pregnancy. Most of these tests cannot detect triploidy, none can detect a balanced rearrangement, and small changes can be missed.

No result was given

About 4 in 100 tests in the pooled data, usually because the sample held too little placental DNA or failed quality checks; one study reported about 1 in 4. A repeat sample can only help if the pregnancy tissue has not yet passed.

Monosomy X or an unusual pattern

This can reflect some of the mother's own cells rather than the pregnancy, so a genetics specialist should interpret it before any conclusions are drawn.

Parental testing

When we suggest a chromosome test for both of you

Testing parents asks whether one of you carries a rearrangement that could affect future pregnancies. UK guidance recommends offering it to both partners in two situations: an unbalanced rearrangement in the pregnancy tissue, or tissue testing that failed or could not be done (RCOG, 2023). The NHS offers the second route only after three or more losses (NHS England GeNotes), and European guidance advises testing only after an individual risk assessment (ESHRE, 2022).

If one of you is a carrier, the outlook remains good. Options to discuss with a genetics team include trying naturally with testing offered during pregnancy, IVF with embryo testing (PGT-SR), or donor eggs or sperm. PGT-SR may mean fewer miscarriages, but evidence that it increases the likelihood of a live birth is lacking (ESHRE, 2022).

We arrange karyotype testing through our partner Jeen Health; it costs £290 for an individual or £550 for a couple, and works best after a conversation with a genetic counsellor. Our parental karyotype guide explains more.

Be prepared

Questions to take to your results appointment

News can be hard to take in, so it helps to write questions down beforehand. You might ask:

Which test was used: a rapid test, a microarray, a karyotype or a blood-based test?

Did the laboratory confirm the sample came from the pregnancy rather than from me?

Is this finding thought to explain the miscarriage, or is its meaning uncertain?

Was it most likely a chance event, or could it have been inherited?

Should either of us have a chromosome test, and would the answer change anything?

Can I have a written copy of the full laboratory report?

NHS and private care

How results reach you on the NHS, and where we fit

On the NHS in England, pregnancy tissue testing is offered from the third miscarriage onwards and, under RCOG guidance, after any loss from 14 weeks; an isolated earlier loss can be tested when particular features point to a chromosome condition. Results usually go back to the clinic that sent the sample. Referral to clinical genetics is not routine, but may be advised when testing identifies a genomic cause or the family has a known genetic condition (NHS England GeNotes; RCOG, 2023).

A partial molar pregnancy should be registered with a specialist trophoblastic disease centre for hCG follow-up (Joyce et al., 2022); in London this is the Charing Cross service. If you would like more time with any result, NHS or private, our genetic counsellors work by video, alongside your NHS care rather than instead of it.

London Pregnancy Clinic

Help from our genetics team

We see patients at our City and West London clinics; genetic counselling happens online, wherever you are.

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Talk your result through

One of Jeen Health's registered genetic counsellors goes through your report with you by video, covering what it could mean next time and whether any further test would help.

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Consultant-led

Clinical genetics consultation

Our consultant clinical geneticist, Dr Harry Leitch, advises on complex findings such as a variant of uncertain significance or a carrier result. Enquire to book.

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When indicated

Parental karyotype

Checks whether either of you carries a rearrangement. Organised with Jeen Health, typically after an unbalanced result or a failed tissue test.

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After repeated losses

Recurrent miscarriage package

Consultant gynaecology review with antiphospholipid and thyroid blood tests, plus a pelvic scan.

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Miscarriage genetic results: your questions

My report says 47,XX,+16. What does that mean?

The pregnancy had 47 chromosomes instead of 46, two X chromosomes (so it was female) and an extra copy of chromosome 16. Trisomy 16 is the most common trisomy found after miscarriage. Like other trisomies it usually arises by chance as the egg matures, and it does not mean either of you carries a chromosome problem.

After a trisomy, is a future baby more likely to have Down's syndrome?

Possibly. A large North American study found that after a miscarriage with a trisomy, the chance of a later pregnancy having a trisomy that can continue, such as Down's syndrome, was about 1.8 times the usual figure for the mother's age (Warburton et al., 2004). Because that usual figure rises with age, the overall chance stays low for most people but is higher for older mothers.

Screening is offered in every NHS pregnancy; see planning a pregnancy after a chromosomal miscarriage for the options.

We were told the change was 'de novo'. What does that mean?

De novo means new: the change was found in the pregnancy but not in either parent's chromosomes, so it arose by chance when the egg or sperm formed or soon after fertilisation. It was not inherited, and neither of you could have known about it or prevented it.

How soon can we try again after a partial molar pregnancy?

Wait until your hCG follow-up has finished. The Charing Cross trophoblastic disease service advises delaying a new pregnancy until then, because a pregnancy could hide the signs in the small number of cases that need further treatment. At Charing Cross, follow-up for a partial mole means blood and urine hCG tests every two weeks until levels are normal, then one confirmatory urine test four weeks later; other centres may differ slightly.

My testing was done at another hospital or a private laboratory. Can you help me understand it?

Yes. A genetic counselling appointment can be used to go through a report from any NHS or private laboratory. Having the full laboratory report to hand, rather than only a summary letter, makes the conversation more useful. If the finding is complex, we may suggest a clinical genetics consultation.

Whatever the result says

Some people feel relief at having an explanation; others feel the loss all over again when the letter arrives. Both are normal. Talking can help: the Miscarriage UK helpline is 0303 003 6464, and Tommy's midwives take free calls on 0800 0147 800.

About this information

This page explains common results in general terms. It cannot interpret your own report or replace advice from the clinicians and genetics professionals caring for you. If you have heavy bleeding, severe pain, a high temperature or feel faint, contact your early pregnancy unit or NHS 111 straight away, or call 999 in an emergency.

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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
RCOGPatient information: Recurrent miscarriage2023
ESHRERecurrent pregnancy loss guideline, update 20222023
NHS England Genomics Education Programme (GeNotes)Presentation: pregnant woman experiencing recurrent miscarriage2026
Tommy'sRecurrent miscarriage2026
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
BMJ (Franssen et al.)Reproductive outcome after chromosome analysis in couples with two or more miscarriages: index-control study2006
Prenatal Diagnosis (Pauta et al.)Genome-wide cell-free DNA analysis for aneuploidy detection in miscarriages: test performance meta-analysis2025
American Journal of Human Genetics (Warburton et al.)Trisomy recurrence: a reconsideration based on North American data2004
BMJ Medicine (Joyce et al.)Advances in the diagnosis and early management of gestational trophoblastic disease2022
Charing Cross Gestational Trophoblast Disease ServiceFollow-up after a molar pregnancyAccessed October 2026