Miscarriage Risk Calculator by Week, Age & Heartbeat

What Is Miscarriage Risk?

Miscarriage risk is the probability that a recognized pregnancy ends in loss before 20 weeks of gestation. Across large population studies, about 10–15% of recognized pregnancies end in miscarriage: the Norwegian registry study by Magnus et al. (BMJ 2019), covering 421,201 pregnancies, measured an overall risk of 12.8%. Many more losses happen before a pregnancy is ever detected, which is why estimates for all conceptions run higher. The reassuring pattern in every dataset is the same: the remaining risk falls steeply as the weeks pass, from roughly 1 in 5 at week 4 to under 1 in 100 by week 12.

This calculator turns that population data into a personal estimate: it starts from your gestational week and day, adjusts for maternal age and the factors you add — a confirmed heartbeat, bleeding, prior losses, BMI — and shows both the estimated risk and the complementary chance of the pregnancy continuing. It is a calm reference point to bring to your provider, not a prediction about your pregnancy. If you are not sure how far along you are, work it out first with the how many weeks pregnant am I calculator, then come back and run your numbers.

How to Use the Miscarriage Risk Calculator

1. Choose how to enter your stage: type your current week and day directly, or switch to due-date mode and enter your due date — the calculator works out your week and day for today automatically. (No due date yet? Get one from the due date calculator.)
2. Enter maternal age — age is the strongest personal factor in the model.
3. Add optional details if you know them: whether a fetal heartbeat has been confirmed, any bleeding or cramping, prior losses or live births, and BMI.
4. Read both numbers: estimated risk and estimated chance of continuing, plus the week-by-week chart showing how your odds improve from here. Use the copy-link button to bookmark your result and watch the number fall as your pregnancy progresses.

How the Miscarriage Risk Estimate Is Calculated

The baseline curve is modeled on the two datasets this page cites throughout: Tong et al. (2008), which followed 697 pregnancies with ultrasound-confirmed heartbeats, and Magnus et al. (2019), the 421,201-pregnancy Norwegian registry study. Your personal factors then scale that baseline up or down. Unlike most calculators, we publish the exact multipliers the model uses — no black box:

The combined multiplier is capped between ×0.25 and ×8.0, and the final estimate is bounded between 0.2% and 85% so extreme input combinations stay within the range the underlying studies actually observed. These are population-level adjustments — a transparent approximation, not a clinical model.

Miscarriage Risk by Week: The Full 4–20 Week Table

The table below is the calculator’s baseline curve: the estimated chance that a pregnancy miscarries from the start of that week onward, before personal factors are applied. Read it as a countdown of reassurance — the risk roughly halves every week between weeks 5 and 8, and drops below 1% at week 12. Our full guide to miscarriage risk by week walks through what changes at each stage.

Baseline modeled on Tong et al. (2008) and Magnus et al. (2019). Two honest caveats: weeks 4–5 carry the widest uncertainty, because many losses at that stage are never confirmed as pregnancies; and losses after 20 weeks are classified as stillbirth, not miscarriage, in most medical systems.

Miscarriage Risk After a Heartbeat Is Seen

Seeing a fetal heartbeat is the single most reassuring milestone of the first trimester. Tong et al. (2008) followed pregnancies after a heartbeat was confirmed on ultrasound and measured the risk of later loss at each week — this is the dataset behind the numbers quoted across the medical web:

Two details from the same study are worth knowing. First, symptoms matter as much as the scan: women with no bleeding or pain whose first visit was at 8 weeks or later had a subsequent loss risk of 1.6% or less. Second, heart rate matters: an embryonic heart rate that is unusually slow for the gestational age (under roughly 100 beats per minute at 6–7 weeks, when 110–160 is typical a week later) is associated with a higher chance of loss — associated, not certain, and one reason providers schedule a follow-up scan rather than giving a verdict on the spot. Our dedicated guide covers miscarriage odds after seeing a heartbeat week by week.

Worked Example: Miscarriage Risk at 8 Weeks

Consider someone 8 weeks pregnant, age 32, with a confirmed fetal heartbeat and no bleeding. The baseline risk at 8 weeks is 2.5%. Age 32 sits in the 30–34 band (×1.15), and the confirmed heartbeat applies ×0.45: 2.5% × 1.15 × 0.45 ≈ 1.3% estimated risk — about 1 in 77 — or a 98.7% chance of the pregnancy continuing. Run the same person at 6 weeks with no heartbeat yet confirmed and the estimate is roughly 10.8% (9.4% × 1.15). Nothing about her changed except two weeks of development and one ultrasound finding — which is exactly how much reassurance time and evidence carry in early pregnancy.

Miscarriage Risk by Age: The Magnus 2019 Table

Maternal age is the strongest known predictor of miscarriage. Magnus et al. (BMJ 2019) linked Norway’s national registries to measure risk across 421,201 pregnancies — the most precise age curve available:

The curve is J-shaped: risk is lowest at 25–29 (9.7%), stays near 1 in 10 through the early 30s, then climbs steeply after 35 as chromosomal errors in eggs become more frequent. Read the right-hand column too — even at 40–44, about 2 in 3 recognized pregnancies do not miscarry. Our full breakdown of miscarriage risk by age goes deeper, including the smaller effect of paternal age.

Miscarriage Risk After Previous Losses

A previous miscarriage raises the statistical risk of another — but by less than most people fear. In Magnus et al. (2019), the age-adjusted odds of miscarriage rose by a factor of 1.54 after one loss, 2.21 after two, and 3.97 after three consecutive losses. Translated into absolute terms against the study’s 12.8% average, that works out to roughly:

Hold onto the right-hand column: even after three losses, the odds still favor the next pregnancy continuing — and with a recurrent-loss workup and supportive early care, outcomes improve further. Two or more consecutive losses is the usual threshold for asking your provider about an evaluation for treatable causes such as thyroid disease, uterine structure, or antiphospholipid syndrome.

How Miscarriage Risk Falls Day by Day

Risk does not drop in weekly steps — it falls a little every day. Between 6 weeks 0 days and 7 weeks 0 days, the baseline remaining risk slides from 9.4% to 4.2%, roughly 0.7 percentage points per day; between weeks 7 and 8 it falls by about 0.24 points per day. Flipping the framing, the odds of not miscarrying climb from 90.6% at 6 weeks to 95.8% at 7 weeks and 97.5% at 8 weeks. Here is the calculator’s day-by-day interpolation for the two steepest weeks:

That daily slope is why this calculator accepts days as well as weeks, and why bookmarking your result link and re-checking in a few days shows a visibly smaller number. The steepest reassurance gains happen between weeks 6 and 10 — the very weeks when anxiety tends to peak and scans are scarcest. If the wait between appointments feels long, following your pregnancy week by week can help mark the progress you are making.

Miscarriage Risk After IVF

IVF pregnancies are watched from the very beginning, so very early losses — including chemical pregnancies that would never be noticed in natural conception — are counted. That detection effect makes headline IVF loss rates (commonly 10–25% of clinical pregnancies, rising with age) look worse than they are. Once a heartbeat is seen, IVF loss rates at the same maternal age are broadly similar to natural conception, and pregnancies from chromosomally screened (euploid, PGT-A) embryos miscarry less — around 10% or lower in most reports — because the leading cause of early loss has been screened out. Our guide to miscarriage after IVF covers fresh vs frozen transfers and what early hCG monitoring can and cannot tell you; you can also track your levels with the hCG level checker.

What the Miscarriage Risk Numbers Can and Cannot Tell You

What they can do: give you honest context. If you are 10 weeks along with a confirmed heartbeat, the data genuinely support reassurance — and many people find that calming during the long wait between appointments. What they cannot do: predict your pregnancy. No online model sees your ultrasound, your lab trends, or your history the way your provider does. If your estimate and your clinician’s assessment ever differ, your clinician is working from more information and is the one to listen to.

It also helps to know what does not cause miscarriage: ordinary stress, moderate exercise, sex, working, or a single cup of coffee. Most early losses stem from chromosomal abnormalities — random, unpreventable, and no one’s fault. If guilt is part of what brought you here, please hear this clearly: you did not cause this by living your life. For a different angle on the odds, our pregnancy chance calculator estimates the likelihood of conceiving in the first place.

The Most Common Causes of Early Miscarriage

About half of first-trimester miscarriages are caused by chromosomal abnormalities — random errors in the embryo’s genetic blueprint that make development impossible. These are not inherited, not caused by anything the parents did, and not preventable. The American College of Obstetricians and Gynecologists (ACOG) lists the other recognized contributors: uterine or placental problems, uncontrolled thyroid disease or diabetes, certain infections, and — less commonly — structural issues or blood-clotting disorders such as antiphospholipid syndrome.

Lifestyle factors play a smaller role than many fear: smoking is the clearest modifiable risk, while moderate caffeine, exercise, and everyday activities have not been shown to cause miscarriage in healthy pregnancies. If you have had recurrent losses, your provider can investigate treatable causes — but after a single early loss, the most likely explanation remains a random chromosomal error.

What Is a Chemical Pregnancy?

A chemical pregnancy is a very early miscarriage that happens before about 5 weeks — after a positive test (hCG is produced, hence “chemical”) but before anything can be seen on ultrasound. As ACOG explains, bleeding from a chemical pregnancy usually occurs around the time of the expected period. Chemical pregnancies are common: by some estimates they account for a large share of all very early losses, and many are noticed only as a slightly late, heavier period by people who were not testing early. They are the main reason the week-4 baseline in our table is high and uncertain. A chemical pregnancy is a real loss and it is normal to grieve it; it does not, by itself, meaningfully raise the risk for your next pregnancy. Falling or plateauing hCG is how clinicians usually confirm one — our hCG doubling time calculator explains the expected pattern.

Types of Miscarriage and What to Expect

Clinicians describe several patterns. Threatened miscarriage means bleeding with a closed cervix — the pregnancy may continue normally, and many do. Missed miscarriage means the embryo stopped developing without symptoms, usually discovered at an ultrasound. Inevitable, incomplete, and complete miscarriage describe whether the cervix has opened and whether all pregnancy tissue has passed.

Physically, a first-trimester miscarriage often feels like a heavy period with stronger cramping; bleeding can last one to two weeks. Management depends on the situation: watchful waiting, medication to help the uterus empty, or a brief procedure — ACOG’s patient guide walks through all three options and their trade-offs. Your provider will recommend based on how far along you are and your preferences — there is rarely a single “right” choice, and asking questions is always appropriate.

Recovery is both physical and emotional. Bleeding usually resolves within two weeks, and most providers suggest waiting until after one normal period before trying again — partly for dating the next pregnancy, partly to give you time. Emotionally, there is no timeline: grief, relief, guilt, and numbness can all coexist, and all are normal. Be as patient with yourself as you would be with a friend.

Thinking About Trying Again

After one miscarriage, the chance of a healthy next pregnancy remains high — most people who miscarry go on to have successful pregnancies, with recurrence risk only modestly elevated (about 19.8% after one loss, per the table above, meaning roughly 4 in 5 next pregnancies do not miscarry). Medically, many providers say it is fine to try again once bleeding has stopped and you feel emotionally ready; the old advice to wait several months is not supported by strong evidence for most cases.

After two or more consecutive losses, guidelines generally recommend a recurrent-loss evaluation to check for treatable causes — the Royal College of Obstetricians and Gynaecologists (RCOG) sets out what that investigation should include. A preconception visit is a good idea at that point: it is a chance to review medications, update vaccinations, start folic acid (400–800 mcg daily is the standard preconception recommendation), and make a monitoring plan that gives you extra reassurance scans early in the next pregnancy.

Support and Resources After Pregnancy Loss

Whether you are here out of curiosity, anxiety, or grief, you deserve support. Your OB provider or midwife is the best first contact — for medical questions and for referrals to counseling. Many countries have dedicated pregnancy and infant loss organizations offering helplines, support groups, and resources for partners too, because grief touches everyone involved.

If you have experienced a loss: take the time you need, lean on people you trust, and know that seeking counseling is a sign of strength, not weakness. If anxiety about this pregnancy is interfering with your daily life, tell your provider — perinatal anxiety is common, treatable, and nothing to be embarrassed about.

When to Seek Care

Contact your provider or seek urgent care for heavy bleeding (soaking a pad within an hour), severe pain or cramping, passing tissue, dizziness or fainting, shoulder pain, or fever — the warning signs the NHS miscarriage guidance tells patients to act on immediately. Shoulder pain and dizziness in particular can signal an ectopic pregnancy, which needs urgent assessment. And remember: you never need to meet a symptom threshold to call. If something feels wrong, that alone is reason enough — this calculator should never delay care.

Sources and References

• Magnus MC, Wilcox AJ, Morken NH, Weinberg CR, Håberg SE. Role of maternal age and pregnancy history in risk of miscarriage: prospective register based study. BMJ 2019;364:l869. 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 first antenatal visit. Obstetrics & Gynecology 2008;111(3):710–714. doi.org/10.1097/AOG.0b013e318163747c
• American College of Obstetricians and Gynecologists (ACOG). Early Pregnancy Loss. Practice Bulletin No. 200, 2018 (reaffirmed since) — clinical definitions, causes, and management. acog.org — Practice Bulletin No. 200
• American College of Obstetricians and Gynecologists (ACOG). Early Pregnancy Loss — patient FAQ on symptoms, treatment options, recovery, and trying again. acog.org — Early Pregnancy Loss FAQ
• NHS. Miscarriage — patient guidance on symptoms, diagnosis, treatment, and when to seek urgent care. nhs.uk/conditions/miscarriage
• Royal College of Obstetricians and Gynaecologists (RCOG). Early miscarriage — patient information on diagnosis, treatment choices, and recovery. rcog.org.uk — Early miscarriage
• Royal College of Obstetricians and Gynaecologists (RCOG). Recurrent Miscarriage. Green-top Guideline No. 17 — the investigation and treatment pathway after repeated losses. rcog.org.uk — Green-top Guideline No. 17

This page’s baseline curve and multipliers are modeled on the studies above; where studies report ranges rather than points, this page says so. Last reviewed October 23, 2026.