What this page is, and what it is not
It is a reference table with its sources attached. Every number on it was copied unchanged from a named published study, and each one is shown with the population that study measured.
It is not a predictor. It will not take your age, your week and your history and give you a personal percentage, and the next section explains why — not as a disclaimer, but because the reason is genuinely worth understanding before you read any figure on any site.
If you have just lost a pregnancy, or you are afraid you are losing one, the most useful things on this page are probably the two sentences about cause further down and the support organisations at the bottom. The arithmetic can wait.
Why no honest tool combines these numbers
There are three well-known sets of miscarriage figures and they are constantly presented as though they slot together. They do not, because they count different things.
| Figure | Who was counted | Counted from |
|---|---|---|
| By age | Every registered pregnancy in a national population | The point of registration |
| By week | Women with no symptoms whose scan that week was normal | That scan |
| By history | A comparison against a woman's own earlier pregnancy | Adjusted for age |
Three different denominators. Multiply a figure from the first row by one from the second and you get a number describing a group of people who do not exist: simultaneously everyone in a national register and only the subset who have already had a reassuring scan.
The week-by-week figures are the ones most often misused, because the condition attached to them gets dropped somewhere between the paper and the blog post. They are conditional on a normal ultrasound having already been seen at that week. They are not the odds at the start of a pregnancy, and quoting a 1.5% figure at eight weeks to someone who has not had a scan is quoting a number from a study she is not in.
By maternal age
From Magnus and colleagues, BMJ 2019;364:l869 — a registry study of 421,201 pregnancies in Norway between 2009 and 2013. It is one of the largest studies of its kind, and because it counts pregnancies from the point they were registered with the health service it catches losses that a clinic-based study would miss.
| Age | Miscarriage rate |
|---|---|
| Under 20 | 15.8% |
| 20–24 | 11.3% |
| 25–29 | 9.8% |
| 30–34 | 10.8% |
| 35–39 | 16.7% |
| 40–44 | 32.2% |
| 45 and over | 53.6% |
| All ages | 12.8% |
The shape is a J. Raised in the teens, lowest through the late twenties — the study reports the single lowest point at age 27, at 9.5% — and then rising close to linearly after 30, steeply after 40.
These are population figures. A 38-year-old is in a band where 16.7% of registered pregnancies ended in miscarriage; the great majority of pregnancies in that band did not.
By gestational week
From Tong and colleagues, Obstetrics & Gynecology 2008;111(3):710–714 — about 700 women in Australia, all of them without symptoms, all of them after a normal first-trimester scan.
The condition is the whole point of the table, so it is worth stating once more before reading it: these are the odds of a loss after this week, given that a scan at this week was normal and there are no symptoms.
| Week | Risk of loss after this point |
|---|---|
| Week 6 | 9.4% |
| Week 7 | 4.2% |
| Week 8 | 1.5% |
| Week 9 | 0.5% |
| Week 10 | 0.7% |
Week 10 comes out very slightly higher than week 9, and it is reproduced that way rather than smoothed into a tidy downward line. In a cohort of around 700 women a difference of two tenths of a percentage point is a handful of pregnancies, and quietly adjusting a published figure to look neater is how a reference table stops being a reference.
Two things the table does not cover: weeks before 6 and after 10, because the study did not; and anyone with bleeding or pain, because the study excluded them by design.
After a previous miscarriage
From the same 2019 registry study. These are odds ratios, adjusted for maternal age:
| Previous consecutive miscarriages | Adjusted odds ratio | 95% confidence interval |
|---|---|---|
| 1 | 1.54 | 1.48–1.60 |
| 2 | 2.21 | 2.03–2.41 |
| 3 or more | 3.97 | 3.29–4.78 |
An odds ratio is not a risk. 1.54 does not mean a 54% chance of anything. It means the odds are about one and a half times those of the comparison group, and what that works out to as a percentage depends entirely on what the comparison group's odds were.
Worked through: if you take a baseline risk of 10%, the odds are 1 to 9. Multiply by 1.54 and the odds become 1.54 to 9, which is a risk of 14.6% — not 15.4%, and nowhere near 54%. At a baseline of 50% the same ratio gives 60.6%, not 77%. The gap between an odds ratio and a risk ratio widens as the baseline rises, which is exactly why they are reported separately.
The calculator above will do that arithmetic for a baseline you choose, and label it as an illustration. It will not pick the baseline for you, because the age bands in the first table already contain women with previous losses, so using one of them as the baseline for this ratio double-counts them.
How common repeated loss is
From the Lancet series on miscarriage (Quenby and colleagues, 2021), which pooled studies across populations:
- about 10.8% of women have had one miscarriage;
- about 1.9% have had two;
- about 0.7% have had three or more.
ACOG puts repeated miscarriage — two or more in a row — at about 5 in 100 women. The reason those two framings differ is that they are counting slightly different groups, and the reason both are worth stating is that a woman who has had two consecutive losses is often told, wrongly, that her situation is vanishingly rare.
The same review puts the overall rate of miscarriage in recognised pregnancies at 15.3%, a little above the 12.8% from the Norwegian register — the difference is mostly about which pregnancies count as recognised and how early they are captured.
What causes it
Most first-trimester miscarriages are caused by a chromosomal problem in the pregnancy — an error that occurred at conception, that could not have been prevented, and that has nothing to do with anything the pregnant person did or did not do.
That sentence is in the NHS guidance, in the ACOG guidance and in every major clinical source, and it is there because the opposite belief is extraordinarily common and, in the large majority of cases, simply wrong. Lifting something, a stressful week, an argument, a glass of wine before you knew, travelling, working, exercising — these are the things people go over afterwards, and they are almost never the reason.
The NHS puts about three quarters of miscarriages in the first trimester. A substantial further share of conceptions are lost before a pregnancy is ever recognised at all; no figure on this page counts those, and no page can tell you about them.
Where to get support
These organisations exist specifically for this, and none of them will think you are overreacting.
- The Miscarriage Association (UK) — helpline, live chat and a support network. miscarriageassociation.org.uk
- Tommy's (UK) — midwife-staffed line and information on recurrent loss. tommys.org
- Share Pregnancy & Infant Loss Support (US). nationalshare.org
- Your GP, midwife or local early pregnancy unit — for anything happening now, this is the first call, not the last.
Sources
-
Magnus MC, Wilcox AJ, Morken N-H, Weinberg CR, Håberg SE. Role of maternal age and pregnancy history in risk of miscarriage: prospective register based study.
BMJ 2019;364:l869.
421,201 registered pregnancies in Norway, 2009–2013
https://www.bmj.com/content/364/bmj.l869 -
Tong S, Kaur A, Walker SP, Bryant V, Onwude JL, Permezel M. Miscarriage risk for asymptomatic women after a normal first-trimester prenatal visit.
Obstetrics & Gynecology 2008;111(3):710–714.
Around 700 asymptomatic women in Australia who had already had a normal first-trimester scan
https://pubmed.ncbi.nlm.nih.gov/18310375/ -
Quenby S, Gallos ID, Dhillon-Smith RK, et al.. Miscarriage matters: the epidemiological, physical, psychological, and economic costs of early pregnancy loss.
The Lancet 2021;397(10285):1658–1667.
Systematic review and meta-analysis
https://pubmed.ncbi.nlm.nih.gov/33915094/ -
NHS. Miscarriage.
nhs.uk.
https://www.nhs.uk/conditions/miscarriage/ -
American College of Obstetricians and Gynecologists. Repeated Miscarriages.
ACOG FAQ.
https://www.acog.org/womens-health/faqs/repeated-miscarriages
This page reproduces published population statistics with their sources attached. It is not medical advice, not a diagnosis and not a prediction about any particular pregnancy. For anything about your own situation, speak to a midwife, GP or obstetrician.
Frequently asked questions
What is the chance of miscarriage at my age?
The largest recent study — Magnus and colleagues in the BMJ in 2019, covering 421,201 registered pregnancies in Norway — found 12.8% overall, with the lowest rate in the late twenties and a rise after 30. By band: under 20, 15.8%; 20–24, 11.3%; 25–29, 9.8%; 30–34, 10.8%; 35–39, 16.7%; 40–44, 32.2%; 45 and over, 53.6%. Those are population figures for everyone in each band, not a prediction about any individual pregnancy.
What is the chance of miscarriage by week?
The well-known week-by-week figures come from Tong and colleagues in 2008 and they answer a narrower question than they are usually quoted as answering. In women with no symptoms who had already had a normal first-trimester scan, the risk of loss after that point was 9.4% at 6 weeks, 4.2% at 7, 1.5% at 8, 0.5% at 9 and 0.7% at 10. The condition matters enormously: these are not the odds at the start of a pregnancy, they are the odds once a heartbeat has already been seen.
Can you combine my age, my week and my history into one number?
No, and this page will not do it even though every other calculator seems happy to. The three sets of figures come from different studies measuring different populations with different denominators — a national register of all pregnancies, a small cohort of women who had already had a reassuring scan, and an age-adjusted comparison against a woman's own earlier pregnancies. Multiplying them produces a number that describes no real group of people. The page shows each figure separately with its source attached.
Does a previous miscarriage make another one more likely?
The same 2019 study found the odds rise with each previous loss: an age-adjusted odds ratio of 1.54 after one, 2.21 after two and 3.97 after three or more consecutive miscarriages. An odds ratio is not a risk — 1.54 does not mean 54% — it means the odds are about one and a half times those of the comparison group, whatever that group's odds happen to be at the same age. The page shows what that implies for a baseline you choose, and labels it as an illustration.
How common is recurrent miscarriage?
The Lancet series on miscarriage (Quenby and colleagues, 2021) pooled studies and found about 10.8% of women have had one miscarriage, 1.9% two, and 0.7% three or more. ACOG puts repeated miscarriage — two or more in a row — at about 5 in 100 women. It is much less common than a single loss, and it is common enough that specialist investigation exists for it.
When does the risk drop?
Sharply through the first trimester. The NHS puts about three quarters of miscarriages in the first twelve weeks. In the Tong data, the risk after a normal scan falls from 9.4% at six weeks to around 1% by weeks nine and ten — most of the drop happens in the fortnight after a heartbeat is first seen.
Why did this happen?
Most first-trimester miscarriages are caused by a chromosomal problem in the pregnancy that could not have been prevented and was not caused by anything you did. The NHS, ACOG and every other major body say this plainly, and they say it because the belief that something a person did caused their miscarriage is both extremely common and, in the large majority of cases, wrong.
I am bleeding. What do these numbers mean for me?
Nothing useful, and this page is not the right place to be. Every figure here is for women without symptoms. Bleeding or pain in pregnancy changes the picture substantially and is a reason to contact your midwife, GP or a local early pregnancy unit today. A calculator cannot examine you or scan you, and the people who can will not mind you calling.
Why do different sources give different overall rates?
Mostly because they count from different starting points. A figure of 10–15% counts recognised pregnancies; higher figures include very early losses detected by sensitive testing that would otherwise never have been noticed as a pregnancy at all. The 2019 registry study reports 12.8% and the 2021 Lancet pooled analysis 15.3%, and neither is wrong — they are measuring slightly different things.
Is this medical advice?
No. This page reproduces published population statistics with their sources attached so you can read them and take them to someone who can talk about your own situation. Nothing here is a diagnosis, a prediction, or advice about a particular pregnancy.