You just saw the flicker on the screen. Maybe it was this morning, maybe an hour ago — and now it is the middle of the night and you are searching for the numbers. Here is the short answer first: once a fetal heartbeat has been seen on ultrasound, the risk of miscarriage falls steeply with every week that passes, from 9.4% at 6 weeks to 0.5% at 9 weeks in a widely cited study of 697 pregnancies (Tong et al., Obstetrics & Gynecology, 2008). Put the other way round, at least 9 out of 10 pregnancies continue even after the earliest possible scan. Our miscarriage risk calculator turns these study figures into an estimate for your exact week, and this page explains where the numbers come from and what can shift them. (Updated 2026.)
The Week-by-Week Odds After a Heartbeat Is Seen
The clearest week-by-week data comes from Tong et al. (2008), who followed 697 women scanned in early pregnancy and recorded the outcome of each pregnancy. Once a heartbeat was seen, the risk of a later miscarriage dropped sharply between 6 and 9 weeks:
| Week the heartbeat was seen | Risk of miscarriage after that scan | Chance the pregnancy continues |
|---|---|---|
| 6 weeks | 9.4% | 90.6% |
| 7 weeks | 4.2% | 95.8% |
| 8 weeks | 1.5% | 98.5% |
| 9 weeks | 0.5% | 99.5% |
| 10 weeks | 0.7% | 99.3% |
Read the middle column like this: out of every 1,000 women who saw a heartbeat at 6 weeks, about 94 later miscarried — and 906 did not. By 8 weeks the figure is about 15 in 1,000, and by 9 weeks about 5 in 1,000. The small uptick at 10 weeks (0.7% versus 0.5% at 9 weeks) sits within the statistical noise of a 697-woman sample and does not mean risk rises again; the honest reading is that the risk plateaus at a very low level from about 9 weeks onward.
Why the 6-Week Risk (9.4%) Is Still Relatively High
The 6-week figure is higher because a heartbeat at 6 weeks has only just switched on. The embryonic heart begins beating at around 6 weeks of gestation, so a scan at this stage catches some embryos in their first days of cardiac activity — including embryos whose development is already faltering, most often for chromosomal reasons, and will stop within days. Between 6 and 8 weeks the embryo also passes through organogenesis, the stage when the major organs form and when development is at its most error-sensitive. An embryo that is still growing with a heartbeat at 8 weeks has cleared most of those early checkpoints, which is why the risk falls so fast between the 6-week and 8-week scans. It is also why a repeat scan one week later tells you so much more than the first one did.
No Bleeding and No Pain? Your Odds Are Better Still
Symptoms change the picture. In the same Tong et al. (2008) study, women who reached 8 weeks or beyond with a heartbeat and no symptoms — no vaginal bleeding and no significant pain — had a subsequent risk of miscarriage of 1.6% or less. In other words, an 8-week scan showing a heartbeat, in a pregnancy that feels uneventful, carries odds of continuing of roughly 98.4% or better. The absence of symptoms is not a guarantee, and symptoms come and go for many harmless reasons, but as a single data point it is a reassuring one. For the full week-by-week risk curve — including the weeks before a heartbeat can be seen at all — see our breakdown of miscarriage risk by week.
Does the Baby's Heart Rate Matter?
Yes — the rate itself carries information, not just the fact that a heartbeat exists. A slow embryonic heart rate, under about 100 beats per minute (bpm) at 6 to 7 weeks, is associated with a higher risk of subsequent loss. The typical embryonic heart rate climbs quickly across these weeks, reaching roughly 110–170 bpm by 7 to 9 weeks. Two things are worth holding onto here. First, "associated with" is not the same as "decides": some embryos with a slow early rate speed up and do fine. Second, a measurement taken at exactly 6 weeks may catch a heart that started beating only a day or two earlier and is still ramping up. If your scan report mentions a low heart rate, the usual plan is a repeat scan in about a week to check that the rate has risen — ask your provider what number they recorded and what happens next.
What If You Bleed After Seeing a Heartbeat?
Bleeding after a heartbeat has been seen does raise the risk of miscarriage compared with having no bleeding — but many pregnancies with first-trimester bleeding still continue, particularly once cardiac activity has been confirmed. Light spotting also has plenty of benign causes, including cervical irritation after an internal scan or an examination. What you should do is straightforward: contact your provider the same day for any bleeding, so they can decide whether you need another scan or blood tests, and seek urgent care for heavy bleeding (soaking through a pad in an hour), severe or one-sided abdominal pain, shoulder-tip pain, or feeling faint. You do not need to panic, and you do need to be checked — both are true at once. If you are comparing your situation with the usual baselines, our guide to miscarriage risk by age shows how age shifts the starting odds, and if you conceived through fertility treatment, miscarriage risk after IVF covers how the timeline works from transfer day.
How a Heartbeat Fits Into the Overall Miscarriage Picture
Zoom out, and the context is this: about 10–15% of recognized pregnancies end in miscarriage overall (ACOG). That headline figure includes the many losses that occur before any scan takes place — often before a heartbeat could ever have been seen. A heartbeat is usually first visible on a transvaginal ultrasound at around 6 weeks, occasionally a few days earlier or later depending on when you ovulated. That is why the after-heartbeat numbers look so much better than the overall rate: reaching the scan and seeing cardiac activity already moves you past the highest-risk window. If your dates are uncertain, the ultrasound due date calculator helps you work out how far along you actually are, and if you are still at the blood-test stage, the hCG level checker explains how rising hCG fits alongside these scan milestones.
Turning Study Averages Into Your Own Estimate
The Tong et al. figures are averages across 697 pregnancies; your personal risk also depends on your age, your medical history, whether you have symptoms, and the heart rate recorded at your scan. Averages are a starting point, not a verdict on your pregnancy — no table can see your scan, and no percentage, reassuring or worrying, is a promise. Use the numbers here to walk into your next appointment with better questions: What was the heart rate? When is the follow-up scan? Does anything in my history change the estimate?
If you are reading this at 2 a.m., the honest summary is the one you came for: seeing a heartbeat is genuinely good news, the odds improve steeply with every week that passes, and by 8 to 9 weeks the large majority of pregnancies with a heartbeat — 98.5% to 99.5% in the Tong data — go on to continue. If you have bleeding, pain, or a worry that will not settle, call your provider; that is what they are there for. And when you want the numbers adjusted to your own week and situation, you can run your own numbers by week and heartbeat in about ten seconds.