Miscarriage Risk Calculator
Estimate your statistical chance of a continuing pregnancy by gestational week and maternal age — and understand what those numbers really mean.
Medically reviewed by Dr. Ruqaiya Khan, MD, FACOGEstimate your risk
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How to read your result
This tool combines two of the strongest, best-documented influences on miscarriage risk: how far along you are and your age. As a pregnancy progresses week by week, the risk of loss falls steeply — and once a heartbeat is confirmed on ultrasound, it drops even further. Your age and your history of previous losses adjust the estimate up or down.
The result is a population-level statistic, not a personal prediction. It describes what tends to happen across large groups of pregnancies with similar characteristics. It cannot tell you what will happen in your pregnancy, and a higher-than-average number does not mean a loss is likely — the great majority of pregnancies with a detected heartbeat go on to be healthy.
If you have symptoms, contact your provider
This calculator is for information and reassurance only. Bleeding, cramping, or a sudden loss of pregnancy symptoms should always be assessed by your midwife or doctor — not by an online tool. If bleeding is heavy or you feel unwell, seek urgent care.
Miscarriage risk by week
Roughly 1 in 7 to 1 in 10 recognised pregnancies ends in miscarriage, and around three-quarters of those losses happen in the first trimester. But that overall figure hides an enormous week-by-week decline: risk is highest in the earliest weeks and falls sharply as the pregnancy establishes itself.
| Gestational stage | Approx. miscarriage risk | What’s happening |
|---|---|---|
| Weeks 3–4 | 50–75% of fertilised eggs | Most losses occur before or around a missed period (often unnoticed) |
| Weeks 5–6 (positive test) | ~15–20% | hCG rising; sac may be visible |
| Week 6 + heartbeat | ~5–9% | Cardiac activity confirmed |
| Week 7 + heartbeat | ~4–5% | First-trimester scan window |
| Week 8 + heartbeat | ~1.5–3% | Strong sign of healthy development |
| Weeks 10–12 | ~2% | Approaching the end of the first trimester |
| After 12–14 weeks | ~1% | Risk now low and continuing to fall |
| After 20 weeks | Defined as stillbirth | Loss after 20 weeks is classified differently |
Miscarriage risk by maternal age
Age is the single strongest age-related factor, mainly because the chance of random chromosomal errors in an egg rises over time. A large Norwegian study of more than 421,000 pregnancies (Magnus et al., BMJ, 2019) found risk was lowest in the late twenties and climbed steeply after the mid-thirties. ACOG’s Obstetric Care Consensus on pregnancy at age 35 and older confirms this pattern clinically and recommends earlier, more detailed counseling on chromosomal screening options for this age group — age-related risk is a reason for tailored prenatal care, not a reason for alarm.
Even at the higher end, it is worth holding two truths together: risk rises with age, and most pregnancies still progress successfully — particularly once a heartbeat has been seen. Paternal age appears to add a smaller, independent effect.
How a detected heartbeat changes everything
Seeing cardiac activity on an early ultrasound is one of the most reassuring milestones in pregnancy. It confirms the embryo has developed far enough to have a beating heart, and it is statistically powerful: once a viable heartbeat is detected around 6–7 weeks, the ongoing risk of loss falls to roughly 5% or lower for most age groups, and continues to drop each week.
Risk after a previous miscarriage
If you have experienced a loss before, it is natural to worry about the next pregnancy. The data show a real but often-misunderstood recurrence pattern. In the Magnus study, compared with women who had not miscarried, the odds of a further loss were about 1.5× higher after one previous miscarriage, roughly doubled after two, and around four times higher after three consecutive losses.
Importantly, even after one or two losses, the majority of women go on to have a successful pregnancy. Professional guidance (ACOG) generally recommends a specialist evaluation for recurrent pregnancy loss — typically defined as two or more — to look for treatable underlying causes.
Had two or more losses?
Ask your provider about a recurrent pregnancy loss assessment. Many identifiable causes (such as certain clotting, hormonal, or uterine factors) can be managed, and most couples ultimately have a healthy baby.
What raises risk — and what doesn’t
Beyond age and history, several factors can modestly influence risk. Just as importantly, many everyday activities that people blame themselves for do not cause miscarriage.
| May increase risk | Does not cause miscarriage |
|---|---|
| Smoking, alcohol, and recreational drug use | Working, normal exercise, and lifting in a typical day |
| Uncontrolled chronic conditions (e.g. diabetes, thyroid, high blood pressure) | Having sex during a healthy pregnancy |
| Certain infections and a very high or very low BMI | Everyday stress, arguments, or a fright |
| Some uterine or hormonal abnormalities | Morning sickness (in fact often a reassuring sign) |
Most first-trimester miscarriages are caused by random chromosomal errors that were present from conception and could not have been prevented. A miscarriage is almost never something you caused or could have stopped.
When to contact your provider
Light spotting is common in early pregnancy and occurs in up to a quarter of healthy pregnancies. Still, certain signs should always be checked promptly. Contact your midwife or doctor if you notice:
- Heavy or bright-red vaginal bleeding, especially with clots
- Strong cramping or persistent lower-abdominal or back pain
- A sudden, complete loss of pregnancy symptoms
- Passing tissue, or fluid leaking from the vagina
- Fever, dizziness, or feeling unwell alongside bleeding
Trust your instincts
If something feels wrong, you are always entitled to be seen. No question is too small, and reaching out early is never an overreaction.
If you are coping with a loss
A miscarriage can be a profound loss, whatever the gestation. Grief is valid, it has no timetable, and there is no “right” way to feel. You don’t have to carry it alone — your care team can talk through what happened and what comes next, and dedicated organisations such as Tommy’s, the Miscarriage Association, and Share Pregnancy & Infant Loss Support offer free, compassionate support. If you are struggling with your mental health, please reach out to your doctor or a trusted person in your life.
How this calculator works
The estimate combines a published week-by-week risk curve with adjustments for maternal age, ultrasound findings, and prior pregnancy history:
- Gestational week sets the baseline remaining risk, following the steep first-trimester decline reported across population studies.
- Maternal age applies a multiplier based on the age bands from Magnus et al. (BMJ, 2019).
- A confirmed heartbeat reduces the estimate, reflecting the lower ongoing risk after viability is seen on ultrasound.
- Previous losses apply a recurrence adjustment in line with the same study.
The result is rounded and deliberately presented as a range-style estimate. It is a simplified statistical model, not a diagnostic tool, and it cannot account for your full medical picture. Always interpret it alongside advice from your own clinician.
Frequently asked questions
How accurate is a miscarriage risk calculator?
Does seeing a heartbeat mean I won’t miscarry?
What week is the safest milestone in pregnancy?
Is spotting in early pregnancy a sign of miscarriage?
Why does miscarriage risk rise with age?
I’ve had a miscarriage before — what are my chances now?
Can stress, working, or exercise cause a miscarriage?
Does this calculator store my information?
Medically reviewed by Dr. Ruqaiya Khan, MD, FACOG
This page was reviewed for medical accuracy by Dr. Ruqaiya Khan. The content is for general education and does not replace personalised advice from your own healthcare provider. Read Dr. Khan’s full profile →
References
- 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.
- American College of Obstetricians and Gynecologists (ACOG). Early Pregnancy Loss. Practice Bulletin No. 200, 2018.
- Tong S, Kaur A, Walker SP, et al. Miscarriage risk for asymptomatic women after a normal first-trimester prenatal visit. Obstet Gynecol. 2008.
- National Health Service (NHS UK). Miscarriage — Overview & Causes. nhs.uk.
- Mayo Clinic. Miscarriage: Symptoms & Causes. mayoclinic.org.
- Tommy’s. Miscarriage statistics and information. tommys.org.
Many people search for a miscarriage risk calculator after a positive test to understand how the odds shift as pregnancy progresses. For more on the medical background behind these statistics, see the ACOG FAQ on early pregnancy loss, and try our hCG Doubling Time Calculator to track your hormone levels alongside your risk estimate.