Miscarriage Calculator 

If you are here, you are probably somewhere between hope and worry, and you deserve numbers that are honest rather than alarming. This miscarriage risk calculator combines five factors that research weighs heavily, maternal age, gestational week, prior losses, heartbeat confirmation, and bleeding, into a single contextual estimate. It is a statistical model, not a diagnosis: nothing here replaces your doctor or midwife, and nothing here can predict an individual pregnancy.

Quick Answer

What this number actually means, and what it cannot do

The percentage above is a population-based estimate: among pregnancies with your combination of factors, roughly this share end in loss. It can give you honest context, especially when the number is low and the waiting between appointments feels endless. It cannot predict your pregnancy. No online model sees your ultrasound images, your lab trends, or your history the way your provider does. Treat the number as background, not as a verdict.

That distinction matters most when the number is high. A high estimate does not mean a loss is expected, and it does not mean anything is wrong right now. It means that, in the groups this model is built from, losses were more common with that combination of factors. If your result worries you, the right next step is a conversation with your provider.

The result is also shown the other way round on purpose: the chance of continuing. A 6.0% risk and a 94.0% continuation chance are the same arithmetic, but they read very differently when you are anxious. Most rival tools show only the risk figure, which reads colder than it needs to. This page leads with both, because both are true.

How the model combines the five factors

The calculator starts from an age-based baseline, then applies four adjustments in order. Nothing is hidden: every factor below is the exact value the tool uses, so you can reproduce any result by hand. This transparency is deliberate. Some competing calculators publish no multipliers at all, which makes their results impossible to check.

Step 1, age baseline. The baseline is drawn from published age ranges and the large Norwegian cohort study by Magnus and colleagues: about 10% under 30, rising through the 30s, and 60% at 45 and over in this model. The exact model values are in the table below, computed from the tool formula, not rounded from a chart.

Read this table as model inputs, not as clinical rates for any individual. Age is the dominant factor because the share of eggs with chromosomal errors rises steadily from the mid-30s onward, but age alone never decides a pregnancy.

Step 2, gestational-week factor. Most losses happen early, so the remaining risk scales down as the pregnancy progresses. The exact factors the tool uses are:

Note what this table is not: it is not a week-by-week clinical risk chart. It is the scaling the model applies to the age baseline. The fall is steepest in the first trimester, which matches the published pattern, and it flattens in the second trimester, when losses become uncommon.

Step 3, prior losses. Each prior miscarriage multiplies the estimate by 1.25, up to a doubling: one prior loss gives 1.25, two give 1.50, three give 1.75, and four or more are capped at 2.00. Most people who have had one miscarriage go on to have healthy pregnancies, and the modest size of this adjustment reflects that. After repeated consecutive losses, clinical guidelines recommend specialist evaluation for treatable causes, which is a matter for your provider, not for this tool.

Step 4, heartbeat and bleeding. A confirmed heartbeat from week 6 onward halves the estimate, reflecting how strongly that milestone predicts continuation. If you select yes but are before week 6, the tool applies no heartbeat reduction, because a heartbeat is not usually confirmed that early. Bleeding raises the estimate: light spotting multiplies by 1.30, heavy bleeding by 2.00. Light spotting alone is common and often harmless, but it is still worth mentioning at your next appointment.

Step 5, floor and cap. The final estimate is never shown below 0.5% or above 90%. No combination of inputs can produce certainty in either direction, because no model of five factors can be certain about an individual pregnancy. If your inputs hit the cap, read it as the model saying the estimate is very high, not as a prediction.

Worked example: 32, week 8, one prior loss, heartbeat seen

These are the pre-filled values, so pressing Calculate reproduces them exactly. Follow the arithmetic:

Age 32 gives a baseline of 15.6%: 12 plus 1.8 for each of the two years past 30. Week 8 scales that by 0.62, giving 9.7%. One prior loss multiplies by 1.25, giving 12.1%. The confirmed heartbeat halves it to 6.0%, so the estimated chance of continuation is 94.0%, within the typical range. If you are still trying to conceive, our conception rate calculator covers the odds on the other side of the journey, and our fertility rate calculator and IVF conception calculator cover the earlier steps.

What does not cause miscarriage

This matters more than the arithmetic. According to guidance from ACOG and the NHS, ordinary stress, moderate exercise, sex during pregnancy, working, and a single cup of coffee do not cause miscarriage. Most early losses stem from chromosomal abnormalities that are random, unpreventable, and nobody's fault. If guilt is part of what brought you here, please hear this clearly: you did not cause this by living your life.

What does raise risk in the published literature is largely outside personal control: advancing maternal age, and in some studies, smoking, heavy alcohol use, and uncontrolled chronic conditions. Those are topics for a provider conversation, framed as health care, not blame. This tool does not ask about them, and it does not adjust for them, so a result here is never a judgment on your choices.

When to contact your doctor promptly

Contact your provider, midwife, or early pregnancy unit right away for heavy bleeding (soaking a pad an hour for two hours or more), severe cramping or one-sided pelvic pain, dizziness or fainting, fever, or tissue passing vaginally. Light spotting alone is common and often harmless, but it is still worth mentioning at your next appointment. If you are ever unsure whether a symptom needs urgent attention, call and ask: early pregnancy units would rather hear from you early than late.

Do not use this calculator to decide whether to seek care. The bleeding input changes a statistical estimate; it does not triage symptoms. Heavy bleeding with severe pain is a reason to seek care regardless of what any percentage says.

What competing calculators miss

Most rival tools ask for age and week and stop there, ignoring the heartbeat milestone that changes the estimate more than any other single input. Others bury the result in jargon or present a bare percentage with no continuation framing, which reads colder than it needs to. Several also skip the medical disclaimer or the explicit discussion of what does not cause miscarriage.

The strongest competitors publish their full multipliers, and this page now matches that standard by printing every factor the tool uses. Where competitors go further, the gap is honest and worth naming: some add week-and-day granularity, body mass index, cramping, or previous live births as inputs. This tool does not use those factors, and this page does not pretend otherwise. Adding them would change what the tool is, which is a decision for a future update, not something to smuggle into a rewrite.

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