Most chromosome changes behind a miscarriage happen by chance in that one pregnancy, so most couples do not need their own chromosomes tested. A parental karyotype earns its place in particular situations, chiefly after a tissue result showing an unbalanced rearrangement, or when no tissue could be tested.
Our genetic counsellors can help you decide whether testing would add anything for you, alongside your NHS care, and arrange a single or couple karyotype if it would.
Two different questions
The phrase 'genetic testing after miscarriage' covers two separate tests, and each one answers its own question.
Examines the lost pregnancy's own chromosomes, using pregnancy tissue or, in some cases before the pregnancy has passed, a blood-based test. It asks why this pregnancy stopped developing. About half of early miscarriages have a chromosome cause, most of them chance events.
A karyotype from a small blood sample from each partner. The question here is whether one of you carries a rearrangement of your own chromosomes that could affect future pregnancies. It cannot explain why a particular pregnancy ended, and in most couples both results are normal.
The basics
Chromosomes are the packages that hold our genes. Most people have 46, in 23 pairs, and each egg or sperm carries one from every pair. A karyotype is the picture a laboratory makes of a person's chromosomes, lined up in order, from a small blood sample.
In a balanced rearrangement, pieces of chromosome have swapped places or turned round, but nothing is missing or extra. Picture two paragraphs of a document cut and pasted into each other's places: every word is still there, so the document still works. Carriers are therefore usually healthy, and most have no idea until they are tested.
Problems arise when eggs or sperm are made. Each receives only half of a person's chromosomes, so in a carrier some end up with a piece missing or a piece extra. A pregnancy that starts with this unbalanced set may miscarry, particularly when a large amount of genetic material is affected; less often it continues, and the baby may have physical or learning difficulties. Others inherit the usual or the balanced arrangement and can develop normally.
On your report
Your report may use one of these terms. Which chromosomes are involved makes a real difference, so ask a genetics specialist to explain your own result.
About 1 in 625 people
Pieces of two different chromosomes break off and swap places. NHS genetics information puts this kind of balanced translocation at roughly 1 in 625 people. Reports usually write it with a 't', such as t(3;7).
About 1 in 1,000 people
Involves only chromosomes 13, 14, 15, 21 and 22, which have very short top arms. The long arms of two of them join, and the short arms, which hold no important genes, are lost. About three quarters involve chromosomes 13 and 14.
A section turned round
A section of one chromosome breaks off, turns round and reattaches in the same place: pericentric if the section includes the chromosome's centre point, paracentric if not. Some inversions have no effect; others can cause problems when passed on.
Figures from guidance and studies describe groups of couples, not your own chances.
When it helps
UK guidance (RCOG, 2023) and the NHS genomic test directory focus parental testing where it is most likely to help. European guidance (ESHRE, 2022) suggests testing only after assessing each couple's individual risk.
| Your situation | What UK and NHS guidance says | What it usually means for you |
|---|---|---|
| Tissue showed an unbalanced structural rearrangement | Offer both partners a karyotype (RCOG); targeted NHS testing of both parents (code R465) | The clearest reason to test. In one hospital series about a third came from a parent; most others arose new |
| Recurrent miscarriage, but no tissue could be tested (none collected, the test failed or it was stored in formalin) | RCOG advises offering parental karyotypes. NHS R464: 3 or more losses with failed testing and no earlier loss tested, or 5 or more with none tested | Worth discussing, although testing tissue from any future loss is usually more informative |
| Tissue showed a numerical change: a trisomy (for example trisomy 16), monosomy X, or an extra whole set of chromosomes (triploidy) | Not a situation in which RCOG recommends parental testing | Usually a chance event; parental testing is rarely needed unless your genetics team suggests it |
| Tissue tested and no chromosome change found | Not a reason for parental testing on its own | Other causes are more relevant; see recurrent miscarriage. A 'normal female' result may need checking for the mother's own cells |
| A relative carries a known rearrangement, or a family member had an unbalanced chromosome condition | Relatives of a known carrier can be tested through NHS genetics (R465); ESHRE counts family history as a risk factor | Testing is usually appropriate; ask your GP about a genetics referral |
| One or two miscarriages, no tissue result and no family history | Not routinely offered on the NHS | A low chance of finding a carrier, particularly if the woman is over 39 (ESHRE). Talk it through first |
NHS test codes apply in England, and local criteria can change. Your NHS team will confirm what is available to you.
The reasoning
It can seem simpler to check both partners after any miscarriage, but guidelines do not recommend routine testing, for three reasons.
Most couples tested are not carriers. A UK audit of more than 20,000 parents with recurrent miscarriage, cited by the RCOG, found a balanced translocation in fewer than 2 in 100 of the individual parents tested.
A carrier result often changes less than people expect. In a large Dutch study, carrier couples were as likely as non-carriers to have a healthy child, although more had a further miscarriage on the way: about 49 in 100, against 30 in 100 (Franssen et al. 2006).
A parental karyotype cannot explain any one loss. Even in carrier couples, only about a third of miscarriages are caused by the rearrangement (ESHRE 2022). That is why testing the pregnancy comes first where possible, and why NHS guidance calls parental testing without a tissue result of limited use. Some couples still want to know before trying again or starting IVF, and a genetic counsellor can help you weigh it up.
Carrier results
A carrier result can come as a shock, and many couples wonder whose fault it is. It is nobody's: a balanced rearrangement is present from birth, is often passed down a family unnoticed, and is not caused by anything either of you did.
Because nothing is missing, carriers are usually healthy and need no treatment. Some men with a Robertsonian translocation have a lower sperm count, which a fertility specialist can check if conceiving is taking a long time.
Each egg or sperm from the carrier may hold the usual, the balanced or an unbalanced arrangement, and only the unbalanced one causes problems. How often depends on the chromosomes and break points involved, so your own figure should come from a genetics specialist rather than a general statistic.
In the Dutch study, 83 in 100 carrier couples went on to have at least one healthy child. Fewer than 1 in 100 pregnancies in carrier couples were unbalanced and carried on past the first trimester (RCOG 2023). That risk is small but not zero, which is why testing in pregnancy is offered.
The best choice depends on your rearrangement, your age and what matters to you. We do not perform CVS or amniocentesis, but our amniocentesis guide explains both, and we can point you to an NHS or private fetal medicine unit.
The carrier's parents, brothers and sisters may have the same rearrangement, which matters if they are planning a family. In England, relatives of a known carrier can be tested through NHS clinical genetics services, and your genetics team can suggest ways to share the news with them.
The test
Reports from any genetic tests on pregnancy tissue or blood show whether parental testing is likely to help, and which chromosomes to focus on.
Before anything is booked, a genetic counsellor or your NHS team sets out what a karyotype could reveal and where its limits lie.
The laboratory grows some of the blood cells, stains their chromosomes and examines them under a microscope.
If a pregnancy result points to particular chromosomes, a test aimed at them may be added, as some rearrangements are too small to see on a standard karyotype.
A normal result means no balanced rearrangement was seen. A carrier result should lead to an appointment with a genetic counsellor or clinical geneticist.
NHS care
On the NHS, parental testing usually follows a result from the pregnancy. Tissue testing is normally offered from the third miscarriage, and after any miscarriage from 14 weeks (RCOG 2023). If it shows an unbalanced rearrangement, or tissue testing was not possible and you meet the NHS criteria, your hospital team can arrange parental karyotypes free of charge, with a referral to clinical genetics if a carrier is found.
After one or two miscarriages you may not meet these criteria, and some couples in London choose private testing to plan ahead. Knowing the NHS pathway first helps a private test add to your care rather than replace the most informative step, which is often testing tissue from any future loss.
Be prepared
Having these to hand helps our genetic counsellors give you clear advice.
Reports from any genetic testing of pregnancy tissue, including tests that failed or came back as 'normal female' (see understanding your result)
How many miscarriages you have had, roughly when, and how many weeks along each pregnancy was
Any family history of miscarriage, stillbirth, or a child with a chromosome condition or learning disability
Whether either of you has had a karyotype before, for example during fertility treatment
Letters from your early pregnancy unit or recurrent miscarriage clinic
Your plans for next time, such as trying naturally or considering IVF
How we can help
Our genetics services sit alongside your NHS care, and you can share every report with your GP or hospital team. Counselling appointments take place over video, so you can join from home.
Start here
A registered genetic counsellor reviews your history and earlier results with you online, and helps you decide whether parental testing would help. A 60-minute appointment (£140) suits complex histories or a carrier result.
Single or couple
Chromosome analysis from a blood sample, arranged with our genetics partner Jeen Health: £290 for an individual test, £550 when both partners are tested. Our karyotype page explains how to book.
Specialist opinion
If a carrier result or a complicated family history needs a specialist view, you can see Dr Harry Leitch, our Consultant in Clinical Genetics. Enquire for availability.
Wider investigations
Consultant gynaecology assessment with a pelvic scan and bloods including antiphospholipid antibodies and thyroid function. A parental karyotype is not in the standard bloods and can be added when indicated.
Rearrangements are found in both men and women, and can be passed to a pregnancy through the sperm as well as the egg. In a large Dutch study of carrier couples, about 6 in 10 carriers were women and 4 in 10 were men (Franssen et al. 2006). Testing only one of you could therefore miss it, which is why a couple karyotype is usually the more useful choice when testing is indicated.
Usually not. A trisomy, meaning a whole extra chromosome, is normally a one-off error in how an egg or sperm divided, and becomes more common as the woman providing the egg gets older; the parents' chromosomes are usually normal. Very occasionally an extra chromosome 13, 14, 15, 21 or 22 is joined to another through a Robertsonian translocation, and if your report raises this, parental testing may be suggested.
No. It means neither of you carries a visible balanced rearrangement. It does not rule out chance chromosome changes in future pregnancies (the commonest cause of miscarriage), changes too small for a karyotype to show, or single-gene conditions. Non-genetic causes, such as antiphospholipid syndrome or a differently shaped womb, are investigated separately; see recurrent miscarriage.
No. Carrier screening checks individual genes to see whether you both carry the same recessive condition, such as cystic fibrosis. A karyotype looks at the number and structure of your chromosomes. Carrier screening is not designed to find the rearrangements linked with recurrent miscarriage, so one cannot replace the other.
NIPT is a screening test based on placental DNA in the mother's blood. Some genome-wide tests can detect larger missing or extra pieces of chromosome, but NIPT cannot give a definite answer and a high-chance result needs confirming. For known carriers, the established check is a diagnostic test such as CVS or amniocentesis; your genetics team can say whether screening has any role for your rearrangement.
Not directly, but it can show whether either of you carries a rearrangement, which is useful when no tissue was ever tested. Bring any old reports you still have, as an earlier result can still guide which test makes sense now.
Yes. You can book a single or couple karyotype directly. We recommend speaking to a genetic counsellor first, so you know what the result can tell you and any carrier result comes with a plan. If you meet NHS criteria, testing is available free through your hospital team.
Waiting for tests, or taking in a carrier result, can be hard on both partners. Our miscarriage support page lists organisations, including the Miscarriage Association (now Miscarriage UK) and Tommy's, that offer free support.
This page explains general principles and cannot replace advice about your own situation from a doctor, genetic counsellor or clinical geneticist. If you are pregnant or have recently miscarried and notice heavy bleeding, severe tummy pain or a fever, or you feel faint, contact your early pregnancy unit or call NHS 111 straight away; in an emergency, call 999.
Contact
The figures and clinical statements on this page are drawn from the sources below. Guidance evolves — always discuss your individual circumstances with a clinician.
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