Alcohol
Drinking in pregnancy is linked with a higher risk that rises with the amount. A small amount before you knew you were pregnant is very unlikely to have caused it.
Does It Really Matter to Know Why a Miscarriage Happened?
Many people who lose a pregnancy ask whether they caused it. For most early miscarriages, the honest answer is no. Our team explains what usually lies behind an early loss, which everyday worries the evidence clears, and when finding a cause can genuinely help.
About half of early miscarriages happen because the pregnancy formed with the wrong number or arrangement of chromosomes. This is usually a one-off chance event, not caused by anything either parent did.
Was it something I did?
The question that follows almost every miscarriage
After a miscarriage it is very common to go back over every detail: the run, a glass of wine at a friend's birthday, carrying heavy shopping, the difficult week at work. Searching for a reason is part of making sense of a loss, and many people feel guilty even after being told it was not their fault.
The evidence is reassuring. At least half of early miscarriages happen because of something within the pregnancy itself, set at or soon after conception, rather than anything you did or did not do. The single most common reason is a chance error in the pregnancy's chromosomes.
Even so, the NHS is clear that the cause of a miscarriage is not always known. When no reason is found, that is not a sign that you were to blame: the pregnancy charity Tommy's notes that it is very unlikely a miscarriage was caused by something you did or did not do.
If a miscarriage has been diagnosed but has not happened yet
Some testing depends on timing. While the pregnancy is still in the womb, a blood test that reads placental DNA in your bloodstream may be possible, although it is still being evaluated in UK research and is not standard NHS care. Once the pregnancy has passed, testing relies on tissue being collected and sent promptly to a genetics laboratory. If you want a cause looked for, ask before treatment: see testing before a miscarriage completes.
Myths and worries
Things people blame themselves for, checked against the evidence
These are the worries people bring to us most often, and what the evidence says about each one.
| The worry | What the evidence says |
|---|---|
| Exercise, such as running or the gym | It does not appear to raise the risk. Miscarriage UK lists exercise among the things you need not worry about. |
| Having sex | Sex during pregnancy is not associated with early miscarriage (RCOG). |
| Going to work, including full-time work | Ordinary work does not seem to raise the risk, including full-time work and jobs that involve long periods of sitting or standing. Night shifts and long hours have been linked with a higher risk without being shown to cause it, and exposure to hazards such as solvents, lead or radiation may raise the risk. |
| Lifting a toddler, the shopping or heavy bags | Everyday lifting and carrying is not a recognised cause. If your job involves heavy lifting for much of the day, discuss it with your doctor before a future pregnancy. |
| Stress, worry or a hard few weeks | There is no clear evidence that stress causes miscarriage. Studies that find a link struggle to separate cause from effect, because miscarriage and pregnancy after a loss are stressful in themselves. |
| Flying, spicy food, a cold or a cough | None of these appears to raise the risk. Very high fevers and some serious infections are different, and need medical advice in pregnancy. |
| Mixed feelings about being pregnant | Not wanting to be pregnant, or having thought about ending the pregnancy, does not seem to increase the risk. |
| Conceiving soon after a birth or a miscarriage | This does not appear to raise the risk either. |
The honest picture
Alcohol, smoking, caffeine, weight and folic acid
A few factors are genuinely linked with miscarriage. A link means the average risk is higher across large groups of people; it cannot tell you what caused your own loss, and something else entirely may have been responsible.
Smoking
Smoking is linked with a higher risk of miscarriage. If you plan to try again, your GP or practice nurse can help you stop.
Caffeine
More than the recommended amount may increase the risk. RCOG advises less than 200 mg a day, around two cups of tea or instant coffee.
Weight
A BMI above 25 or below 19 is linked with a higher chance of miscarriage (RCOG). Your GP can offer support before a future pregnancy if you would like it.
Folic acid
Folic acid helps prevent spina bifida and other neural tube conditions, but it has not been shown to prevent miscarriage: a Cochrane review of more than 7,000 pregnancies found no clear difference in miscarriage rates. Our folic acid guide covers what to take next time.
The most common cause
Why chromosome changes are the commonest explanation
A pregnancy normally has 46 chromosomes, the packages that carry our genes, half from the egg and half from the sperm. If an egg or sperm forms with one too many or one too few, or the earliest cells divide unevenly, the pregnancy usually cannot develop normally and often ends in miscarriage.
About half of early miscarriages happen this way (RCOG), and about 6 in 10 miscarriages that are tested show a chromosome abnormality (Lancet 2021). The most frequent finding is an extra copy of one chromosome, called a trisomy. Others include a whole extra set of chromosomes, a missing sex chromosome, or a missing or extra piece of a chromosome.
Usually both parents' own chromosomes are normal. These errors become more common as eggs age, but they can happen at any age and are not caused by anything either parent did. Our guide to chromosomal causes of miscarriage explains the different types.
The numbers behind the reassurance
These figures describe large groups of people, not any one pregnancy. Sources are listed at the foot of this page.
Up to 1 in 5 Recognised pregnancies that miscarry in the first three months (RCOG); pooled data suggest about 15 in 100 (Quenby et al., Lancet 2021)
About 1 in 2 Early miscarriages caused by a chromosome change in the pregnancy (RCOG, 2023)
About 6 in 10 Tested miscarriage samples that show a chromosome abnormality (Quenby et al., Lancet 2021)
3 to 6 in 100 Couples with recurrent miscarriage in whom one partner carries a balanced chromosome rearrangement (NICE CKS; RCOG)
Risk factors
Risk factors that nobody chooses
Some things raise the chance of miscarriage but are not choices or mistakes. Our miscarriage statistics page shows how the risk changes with age.
- Age. Chromosome errors become more common as eggs age, so miscarriage is more common from 35 and most common over 40.
- Ethnicity. Women of Black African or Black Caribbean background are more likely to have an early miscarriage, for reasons not yet understood.
- Previous miscarriages. The chance rises with each loss, yet even after three miscarriages most people have a healthy pregnancy next time.
- Medical conditions. Antiphospholipid syndrome, poorly controlled diabetes or thyroid disease, and some differences in the shape of the womb can all play a part.
Does knowing help?
Five ways an answer can make a difference
Not everyone wants to know why a miscarriage happened, and that is a valid choice. For those who do, an answer can matter in practical ways as well as emotional ones.
It can lift the weight of self-blame
A chromosome change usually shows that the pregnancy was affected from its earliest days, by an error as the egg or sperm formed or in the first cell divisions. Exercise, sex, work or stress in the weeks that followed could not have caused that. For many people, a clear explanation replaces the 'what ifs' with something concrete. It does not take the grief away, but it can change how you carry it.
It helps estimate the chance of it happening again
Most chromosome problems in a pregnancy happen by chance and are unlikely to happen again. Once age is taken into account, RCOG guidance notes that a miscarriage caused by a chromosome change is linked with a better outlook next time than one with normal chromosomes, unless a parent carries a chromosome rearrangement.
It shows whether you and your partner need testing
Occasionally the tissue shows an unbalanced rearrangement, where a piece of chromosome is missing or extra. This can come from a healthy parent who carries a balanced version; overall, one partner carries a balanced rearrangement in around 3 to 6 in 100 couples with recurrent miscarriage. RCOG advises offering both partners a karyotype blood test in that situation, or when the tissue could not be tested; see parental chromosome testing.
It can shape your plans for next time
A result helps you and your doctors choose which scans, screening or diagnostic tests make sense in a future pregnancy, and whether to see a genetics specialist. Our guide to pregnancy after a chromosomal miscarriage covers this in more depth.
A normal result points the search elsewhere
A normal chromosome result does not rule out other causes. When miscarriages keep showing normal chromosomes, RCOG guidance suggests an ongoing factor in the mother may be more likely, such as antiphospholipid syndrome, a thyroid problem or the shape of the womb. Those are the investigations to focus on after repeated losses; see recurrent miscarriage.
Being realistic
What a test cannot tell you
Testing does not always give an answer. Tissue is not always collected, and with traditional chromosome analysis the cells fail to grow in the laboratory in around 1 in 5 samples (RCOG). Microarray tests avoid that problem, but a sample can contain the mother's cells instead of the pregnancy's; some microarray tests can check for this.
A normal result does not mean you did something wrong. Some genetic changes are too small to show up on standard tests, other causes may lie in the mother's body, and RCOG notes that recurrent miscarriage very often remains unexplained. Even then, the chance of a successful pregnancy in future is usually good, particularly with supportive care from an experienced team.
On the NHS
When testing is offered on the NHS
Routine NHS investigations usually begin after three or more miscarriages, when your GP can refer you for tests to look for a treatable cause. RCOG guidance is to offer chromosome testing of pregnancy tissue from the third miscarriage onwards, and after any miscarriage in the second trimester. Tommy's notes that, in practice, NHS tissue testing is often limited to people who had surgery, and results can take weeks or months.
Tests can sometimes start after two early miscarriages if your doctor suspects a cause. They usually include blood tests for antiphospholipid syndrome, thyroid tests and a pelvic scan to check the shape of the womb, with parents' chromosomes checked only in specific circumstances.
After a first or second miscarriage, some people choose private testing because they want an answer now, or because tissue is available this time. There is no right or wrong choice.
How we can help
Support from our genetics and gynaecology teams
If understanding why matters to you, we can help alongside your NHS care. Genetic counselling appointments take place online by video; gynaecology appointments are at our clinic in the City of London.
Online, 30 minutes
Genetic counselling
Talk through what happened, whether a test could still help and what a result might mean, with a registered genetic counsellor.
Pregnancy tissue
Tissue testing after miscarriage
If tissue has been or will be collected, we can arrange chromosome analysis through accredited genetics partners after a counselling appointment.
Complex results
Clinical genetics consultation
For unexpected or complex results, or questions about inherited risk, with Dr Harry Leitch, Consultant in Clinical Genetics.
After repeated losses
Recurrent miscarriage package
A consultant gynaecologist assessment, pelvic scan and blood tests that include antiphospholipid antibodies and thyroid function. Booked with a £300 deposit, deducted from the total.
Why did I miscarry? Your questions
Could anything about my partner have played a part?
Chromosome errors can arise in sperm as well as in eggs, and either partner can carry a balanced chromosome rearrangement. The NHS also names a father aged 45 or over as a risk factor. None of this is something either of you chose or could have changed during the pregnancy.
I had a few drinks before I knew I was pregnant. Was that the reason?
A small amount of alcohol before you knew you were pregnant is very unlikely to have caused your miscarriage; Tommy's makes the same point about a couple of drinks. Drinking in pregnancy is linked with a higher risk that rises with the amount, which is why RCOG advises not drinking alcohol when you are planning another pregnancy. That advice is about lowering risk next time, not a verdict on what happened this time.
I hadn't started taking folic acid. Is that why I miscarried?
This is very unlikely to be the reason. Folic acid protects against neural tube conditions such as spina bifida, and trials have not shown that it prevents miscarriage. It is still worth taking when you try again; our folic acid guide explains the dose and timing.
Is it worth having testing after a first miscarriage?
It depends on what would help you. The NHS usually offers tissue testing from the third miscarriage, so after a first loss testing is usually a private choice. Some people want to know straight away, especially if tissue is available now; others prefer to wait. A 30-minute genetic counselling appointment can help you weigh up what a test could and could not tell you.
Could anything have prevented my miscarriage?
When a miscarriage is caused by a chance chromosome change, as about half of early miscarriages are, nothing could have prevented it. For a smaller number of people, tests find a cause that can be treated. For example, people with antiphospholipid syndrome are usually offered low-dose aspirin and heparin injections in their next pregnancy.
Testing found no cause. Does that mean it was something I did?
No. A normal chromosome result means no chromosome change was found in that pregnancy. Other causes, such as a clotting or thyroid condition or the shape of the womb, have nothing to do with how you behaved, and plenty of losses remain unexplained even after thorough tests. Not having an answer is hard, but it is not evidence of blame.
Why do I still feel guilty when I know it wasn't my fault?
Many people feel guilty after a miscarriage, even once the cause has been explained. Talking to your partner, family or friends can help, and your GP or pregnancy unit can tell you about counselling. Miscarriage UK runs a support line on 0303 003 6464, and Tommy's midwives can be reached free on 0800 0147 800, Monday to Friday, 9am to 5pm.
About this information
This page is general information to help you understand why miscarriages happen. It cannot replace advice from a clinician who knows your history. If you have heavy bleeding, severe tummy or shoulder pain, a fever, or you feel faint, contact your early pregnancy unit or call NHS 111, and call 999 in an emergency.
Contact
Would you like to talk through what happened?
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 (patient information)2023
- RCOGEarly miscarriage (patient information)2016
- RCOGRecurrent Miscarriage (Green-top Guideline No. 17)2023
- The Lancet (Quenby et al.)Miscarriage matters: the epidemiological, physical, psychological, and economic costs of early pregnancy loss2021
- NICE Clinical Knowledge SummariesMiscarriage: risk factors2023
- NHSMiscarriage2026
- Tommy'sWhat causes a miscarriage?2026
- Miscarriage UKCauses and risk factors of miscarriageAccessed October 2026
- Tommy'sRecurrent miscarriage2026
- Tommy'sUsing fetal DNA to detect chromosomal abnormalities following miscarriageAccessed October 2026
- Alcoholism: Clinical and Experimental Research (Sundermann et al.)Alcohol use in pregnancy and miscarriage: a systematic review and meta-analysis2019
- Cochrane Database of Systematic Reviews (De-Regil et al.)Effects and safety of periconceptional oral folate supplementation for preventing birth defects2015