Miscarriage Risk Calculator
Use this Miscarriage Risk Calculator to see the chance your pregnancy continues, week by week, based on your age, history and heartbeat scan.
Updated October 20, 2026
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Miscarriage Risk Is Calculated
A miscarriage is the loss of a pregnancy before 20 weeks². About 15 in 100 recognized pregnancies end this way³, but the risk falls quickly as the weeks pass, and most of all once a heartbeat has been seen on a scan¹. This calculator combines figures for your week, age and history.
What Your Result Measures
Your result is the estimated chance that a pregnancy like yours continues past 20 weeks without a miscarriage, from where you are now. It is an average for people with the same week, age and history, so it cannot predict your own pregnancy. The week figures come from women who had no bleeding or pain at the time of their scan¹.
The Formula
Odds = risk / (100 - risk)
Your odds = odds for your week x age factor x history factor
Your risk (%) = 100 x your odds / (1 + your odds)
Chance the pregnancy continues (%) = 100 - your risk
The week figures come from 696 women in Australia whose scan showed a heartbeat¹, and the age and history factors come from 421,201 pregnancies in Norway².
How This Calculator Computes Your Result
Enter how far along you are (weeks and days, or the first day of your last period) and your age. You can also add whether a heartbeat has been seen and how many miscarriages in a row you had before this pregnancy.
Heartbeat seen: it starts from the risk for the week of your latest scan that showed a heartbeat, then adjusts it for your age and history.
Not yet, or not sure: it shows the risk for the pregnancy as a whole, and the figure if a heartbeat were seen now. Your real chance lies between the two.
The age factor compares the rate for your age group with the rate for all ages (12.8%), and the history factor comes from the same study².
One assumption: no study measured week, age and history together. The calculator assumes the age and history effects found for the whole pregnancy apply in the same proportion at every week. This is a working assumption, not a measured fact.
The likely range reflects that the week figures rest on just 11 miscarriages¹.
You see your chance the pregnancy continues, your remaining risk, the likely range, and a week-by-week table for a heartbeat seen at 6, 7, 8, and 9 or more weeks. Results are whole numbers out of 100, and the remaining risk is also shown as a percentage to one decimal place.
What Your Result Means
Once a heartbeat has been seen, the risk falls sharply with each week. These are the figures for all ages, as published¹:
Weeks pregnant when the heartbeat was seen | Risk of miscarriage | Chance the pregnancy continues |
6 | 9.4% | 90.6% |
7 | 4.2% | 95.8% |
8 | 1.5% | 98.5% |
9 | 0.5% | 99.5% |
10 | 0.7% | 99.3% |
The 9 and 10 week figures rest on very few losses, so the calculator uses the more cautious 0.7% from 9 weeks onward. The risk later in pregnancy is likely lower still.
Age also matters. In the Norwegian study, the risk for the pregnancy as a whole was²:
Age | Risk of miscarriage | Chance the pregnancy continues |
Under 20 | 15.8% | 84.2% |
20 to 24 | 11.3% | 88.7% |
25 to 29 | 9.8% | 90.2% |
30 to 34 | 10.8% | 89.2% |
35 to 39 | 16.7% | 83.3% |
40 to 44 | 32.2% | 67.8% |
45 and over | 53.6% | 46.4% |
Previous miscarriages raise the risk too. In the same study, the risk was 11.6% in a first pregnancy, 19.8% after one miscarriage, 27.7% after two in a row and 41.9% after three or more². Pooled data from several countries show similar figures³. Even so, about 65 in 100 women with repeated miscarriages and no cause found have a successful next pregnancy⁵.
What Does Not Cause Miscarriage
About half of early miscarriages happen because the pregnancy has a problem with its chromosomes⁴. Miscarriages are almost never caused by anything you did or did not do⁵. There is no evidence that stress or having sex during pregnancy causes a miscarriage⁶. Beliefs that lifting heavy objects or past use of contraception can cause one are also mistaken³. Bleeding and cramping can be signs of miscarriage, but they are also common in pregnancies that continue normally⁴.
When to Contact a Clinician
These figures are for pregnancies without symptoms. The NHS advises⁷:
Get urgent advice from your maternity unit, early pregnancy unit or doctor (NHS 111 in the UK) if you have light bleeding or spotting, unusual discharge, or fluid leaking from your vagina.
Call 999 or your local emergency number if you have bleeding with severe tummy pain, pain in your shoulder, or you feel sick, faint or dizzy, or if the bleeding is heavy (soaking a pad soon after you put it on).
Miscarriage Risk by Week the Heartbeat Was Seen
The risk of miscarriage after a scan showed a heartbeat, for all ages, by week of pregnancy at that scan.
Show data table
| Weeks pregnant at the scan | Risk of miscarriage (%) |
|---|---|
| 6 weeks | 9.4 |
| 7 weeks | 4.2 |
| 8 weeks | 1.5 |
| 9 weeks | 0.5 |
| 10 weeks | 0.7 |
Miscarriage Risk by Age and Past Miscarriages
The risk for the pregnancy as a whole in the Norwegian study, by age or by miscarriages in a row before this pregnancy.
Show data table
| Age | Risk of miscarriage (%) |
|---|---|
| Under 20 | 15.8 |
| 20 to 24 | 11.3 |
| 25 to 29 | 9.8 |
| 30 to 34 | 10.8 |
| 35 to 39 | 16.7 |
| 40 to 44 | 32.2 |
| 45 and over | 53.6 |
A Note on Accuracy
These are estimates for groups of people, not a diagnosis. The week figures come from one small study of women without symptoms at a hospital clinic¹, and the registry behind the age figures likely missed some very early losses², so risk before about 6 weeks may be higher than shown. If a scan did not show a heartbeat when one was expected, this calculator cannot interpret that result. Your care team can.
Frequently Asked Questions
What are the chances of miscarriage week by week?
Once a heartbeat has been seen, one study found the risk fell from 9.4% at 6 weeks to 4.2% at 7 weeks, 1.5% at 8 weeks and under 1% at 9 to 10 weeks¹. Your own figure also depends on your age and history.
How common is miscarriage?
About 15 in 100 recognized pregnancies end in miscarriage³. The risk is lowest at ages 25 to 29 and rises with age after 30².
Does age affect the risk of miscarriage?
Yes. In a large Norwegian study, the risk was lowest at ages 25 to 29 (9.8%) and rose to 32.2% at 40 to 44 and 53.6% at 45 and over².
How accurate is a miscarriage risk calculator?
It gives an estimate for groups of people like you, not a prediction for your own pregnancy. It joins figures from different studies using a stated assumption, so treat the result as a guide, not a certainty.
Sources
Miscarriage Risk for Asymptomatic Women After a Normal First-Trimester Prenatal Visit, Tong et al., 2008
Role of Maternal Age and Pregnancy History in Risk of Miscarriage, Magnus et al., 2019
Miscarriage Matters, Quenby et al., 2021
Early Pregnancy Loss (Practice Bulletin No. 200), American College of Obstetricians and Gynecologists, 2018
Repeated Miscarriages, American College of Obstetricians and Gynecologists
Early Miscarriage, Royal College of Obstetricians and Gynaecologists
Miscarriage, NHS