Miscarriage Risk Calculator
Disclaimer: This calculator provides an educational, population-level estimate only. It is not a diagnosis and does not replace medical advice, examination, ultrasound, or lab testing. Estimates may not apply to IVF/assisted reproduction, multiple pregnancy (twins), suspected/known ectopic pregnancy, molar pregnancy, significant medical conditions, or medication exposures.
Getting pregnant is exciting, but worries about miscarriage can naturally cause anxiety. If you’re feeling this way, you’re not alone; many people share the same fears in early pregnancy. Most early miscarriages happen due to chromosomal factors that are beyond anyone’s control. As the weeks pass, the risk drops and reassurance grows.
How to use this calculator
The calculator will be used like;
- Enter the mother’s age (Maternal age).
- Enter the pregnancy week with the day.
- To get an estimate, press enter to see the percentage of risk of miscarriage.
What it can do
- Provide a baseline estimate based on large populations
- Show how risk generally changes by week of pregnancy and age
- Offer reassurance that, for many pregnancies, risk declines rapidly with time
What it can’t do
- Diagnose a miscarriage or confirm viability (that requires clinical evaluation)
- Guarantee a “safe” outcome, even if the number looks low
- Account for every personal factor (genetics, anatomy, infections, rare conditions, etc.)
So think of a miscarriage odds calculator as a context tool, not a verdict.
What is a miscarriage?
A miscarriage means fetal death before 20 weeks of pregnancy. A miscarriage risk calculator tells the probability of fetal death in the current or the coming week. When gestational age reaches 20 week the miscarriage chances decrease rapidly. Gestational age is estimated from the dating ultrasound, as well as from the last menstrual period (LMP).
The Science Behind Miscarriage Risk
The fetus can die from many things, but the known issue is chromosomal abnormalities in the embryo, not from any fruit like jackfruit. You cannot control it. In start, there is a high risk, and as time passes, the risk declines. The first trimester is crucial for the baby’s development. Infections like UTI can also affect you.
About 10% to 20% of known pregnancies end in miscarriage, and the number that I think is higher, as many females don’t know the day of their last period. In NHS notes, a known pregnancy ends in miscarriage.
Guardrails in the calculator
If pregnancy is above 20 weeks, the calculator shows a miscarriage risk of, about 1% and the chance of continuing is about 99%.
Miscarriage Risk by Age
Age affects miscarriage risk largely because the probability of chromosomal abnormalities increases with advanced maternal age. The older the lady, the more the chances of miscarriage increase. The risk was lowest around ages 25–29, increased with older maternal age over 50% at age 45+ in that population. This does not mean older people cannot have healthy pregnancies. It means the starting probabilities differ, largely because chromosomal errors become more common with age.
What Usually Causes a Miscarriage?
Certain medical conditions, like diabetes, can increase the risk of fetal death. Thyroid diseases like hyperthyroidism and hypothyroidism can cause hormonal imbalance, which directly affects the pregnancy. If a female has uterine abnormalities, then she should go to a doctor. Many people say stress or sex during pregnancy can cause the death of the fetus, but that is not true.
RCOG says recurrent miscarriage is defined as three or more first-trimester miscarriages, while also noting that clinicians may consider evaluation earlier depending on context. Recurrent miscarriage affects 1 in 100 women.
A normal baby is connected with the placenta, and the placenta is connected with the womb. Hormones like progesterone help the uterus be strong enough so the placenta can attach without problems, and hcg will start to rise when implantation occurs.
Miscarriage risk generally goes down as pregnancy progresses, and there are two major reassurance milestones people talk about.
- Heartbeat confirmation
- Completing 20 weeks
What week are you safe from miscarriage
There is no week where the risk becomes zero percent. Pregnancy always carries some degree of risk. However, the chance of miscarriage becomes much lower after the first 3 months.
Lifestyle factors
If a female is pregnant and she smokes alcohol abuser or she can’t manage obesity the lead to miscarriage in medical literature. Even if you do everything right miscarriage can occur, so you don’t need to blame yourself.
When to Contact a Clinician Urgently
A calculator can’t evaluate symptoms. Seek medical advice if you have:
- Heavy bleeding
- Severe or worsening pain
- Faintness/dizziness
- Fever or feeling very unwell
Early assessment matters because some urgent conditions (like ectopic pregnancy) can mimic early miscarriage symptoms and need timely care. Clinical guidelines focus heavily on evaluation of pain/bleeding in early pregnancy for this reason.
(This is general education, not a diagnosis.)
Miscarriage Probability Chart
Miscarriage risk chart: remaining probability of miscarriage after reaching each week
| Gestational week reached | Miscarriage Risk Chances | Not Miscarrying Chances |
|---|---|---|
| 3 weeks | 30.0% | 70.0% |
| 3 weeks, 1 day | 29.3% | 70.7% |
| 3 weeks, 2 days | 28.6% | 71.4% |
| 3 weeks, 3 days | 27.9% | 72.1% |
| 3 weeks, 4 days | 27.2% | 72.8% |
| 3 weeks, 5 days | 26.5% | 73.5% |
| 3 weeks, 6 days | 25.7% | 74.3% |
| 4 weeks | 25.0% | 75.0% |
| 4 weeks, 1 day | 24.2% | 75.8% |
| 4 weeks, 2 days | 23.3% | 76.7% |
| 4 weeks, 3 days | 22.5% | 77.5% |
| 4 weeks, 4 days | 21.6% | 78.4% |
| 4 weeks, 5 days | 20.7% | 79.3% |
| 4 weeks, 6 days | 19.9% | 80.1% |
| 5 weeks | 19.0% | 81.0% |
| 5 weeks, 1 day | 18.2% | 81.8% |
| 5 weeks, 2 days | 17.5% | 82.5% |
| 5 weeks, 3 days | 16.7% | 83.3% |
| 5 weeks, 4 days | 15.9% | 84.1% |
| 5 weeks, 5 days | 15.1% | 84.9% |
| 5 weeks, 6 days | 14.3% | 85.7% |
| 6 weeks | 13.5% | 86.5% |
| 6 weeks, 1 day | 12.8% | 87.2% |
| 6 weeks, 2 days | 12.0% | 88.0% |
| 6 weeks, 3 days | 11.3% | 88.7% |
| 6 weeks, 4 days | 10.6% | 89.4% |
| 6 weeks, 5 days | 10.0% | 90.0% |
| 6 weeks, 6 days | 9.4% | 90.6% |
| 7 weeks | 8.7% | 91.3% |
| 7 weeks, 1 day | 8.1% | 91.9% |
| 7 weeks, 2 days | 7.5% | 92.5% |
| 7 weeks, 3 days | 6.8% | 93.2% |
| 7 weeks, 4 days | 6.4% | 93.6% |
| 7 weeks, 5 days | 6.0% | 94.0% |
| 7 weeks, 6 days | 5.6% | 94.4% |
| 8 weeks | 5.2% | 94.8% |
| 8 weeks, 1 day | 4.8% | 95.2% |
| 8 weeks, 2 days | 4.4% | 95.6% |
| 8 weeks, 3 days | 4.1% | 95.9% |
| 8 weeks, 4 days | 3.9% | 96.1% |
| 8 weeks, 5 days | 3.8% | 96.2% |
| 8 weeks, 6 days | 3.6% | 96.4% |
| 9 weeks | 3.5% | 96.5% |
| 9 weeks, 1 day | 3.4% | 96.6% |
| 9 weeks, 2 days | 3.2% | 96.8% |
| 9 weeks, 3 days | 3.1% | 96.9% |
| 9 weeks, 4 days | 2.9% | 97.1% |
| 9 weeks, 5 days | 2.8% | 97.2% |
| 9 weeks, 6 days | 2.6% | 97.4% |
| 10 weeks | 2.5% | 97.5% |
| 10 weeks, 1 day | 2.4% | 97.6% |
| 10 weeks, 2 days | 2.3% | 97.7% |
| 10 weeks, 3 days | 2.3% | 97.7% |
| 10 weeks, 4 days | 2.2% | 97.8% |
| 10 weeks, 5 days | 2.2% | 97.8% |
| 10 weeks, 6 days | 2.1% | 97.9% |
| 11 weeks | 2.1% | 97.9% |
| 11 weeks, 1 day | 2.0% | 98.0% |
| 11 weeks, 2 days | 1.9% | 98.1% |
| 11 weeks, 3 days | 1.9% | 98.1% |
| 11 weeks, 4 days | 1.8% | 98.2% |
| 11 weeks, 5 days | 1.8% | 98.2% |
| 11 weeks, 6 days | 1.7% | 98.3% |
| 12 weeks | 1.7% | 98.3% |
| 12 weeks, 1 day | 1.6% | 98.4% |
| 12 weeks, 2 days | 1.6% | 98.4% |
| 12 weeks, 3 days | 1.5% | 98.5% |
| 12 weeks, 4 days | 1.5% | 98.5% |
| 12 weeks, 5 days | 1.4% | 98.6% |
| 12 weeks, 6 days | 1.4% | 98.6% |
| 13 weeks | 1.3% | 98.7% |
| 13 weeks, 1 day | 1.3% | 98.7% |
| 13 weeks, 2 days | 1.2% | 98.8% |
| 13 weeks, 3 days | 1.2% | 98.8% |
| 13 weeks, 4 days | 1.2% | 98.8% |
| 13 weeks, 5 days | 1.1% | 98.9% |
| 13 weeks, 6 days | 1.1% | 98.9% |
| 14 weeks | 1.0% | 99.0% |
| 14 weeks, 1 day | 1.0% | 99.0% |
| 14 weeks, 2 days | 1.0% | 99.0% |
| 14 weeks, 3 days | 0.9% | 99.1% |
| 14 weeks, 4 days | 0.9% | 99.1% |
| 14 weeks, 5 days | 0.9% | 99.1% |
| 14 weeks, 6 days | 0.8% | 99.2% |
| 15 weeks | 0.8% | 99.2% |
| 15 weeks, 1 day | 0.7% | 99.3% |
| 15 weeks, 2 days | 0.7% | 99.3% |
| 15 weeks, 3 days | 0.7% | 99.3% |
| 15 weeks, 4 days | 0.6% | 99.4% |
| 15 weeks, 5 days | 0.6% | 99.4% |
| 15 weeks, 6 days | 0.6% | 99.4% |
| 16 weeks | 0.5% | 99.5% |
| 16 weeks, 1 day | 0.5% | 99.5% |
| 16 weeks, 2 days | 0.5% | 99.5% |
| 16 weeks, 3 days | 0.5% | 99.5% |
| 16 weeks, 4 days | 0.5% | 99.5% |
| 16 weeks, 5 days | 0.4% | 99.6% |
| 16 weeks, 6 days | 0.4% | 99.6% |
| 17 weeks | 0.4% | 99.6% |
| 17 weeks, 1 day | 0.4% | 99.6% |
| 17 weeks, 2 days | 0.4% | 99.6% |
| 17 weeks, 3 days | 0.3% | 99.7% |
| 17 weeks, 4 days | 0.3% | 99.7% |
| 17 weeks, 5 days | 0.3% | 99.7% |
| 17 weeks, 6 days | 0.3% | 99.7% |
| 18 weeks | 0.3% | 99.7% |
| 18 weeks, 1 day | 0.3% | 99.7% |
| 18 weeks, 2 days | 0.2% | 99.8% |
| 18 weeks, 3 days | 0.2% | 99.8% |
| 18 weeks, 4 days | 0.2% | 99.8% |
| 18 weeks, 5 days | 0.2% | 99.8% |
| 18 weeks, 6 days | 0.2% | 99.8% |
| 19 weeks | 0.1% | 99.9% |
| 19 weeks, 1 day | 0.1% | 99.9% |
| 19 weeks, 2 days | 0.1% | 99.9% |
| 19 weeks, 3 days | 0.1% | 99.9% |
| 19 weeks, 4 days | 0.1% | 99.9% |
| 19 weeks, 5 days | 0.1% | 99.9% |
| 19 weeks, 6 days | 0.0% | 100% |
| 20 weeks | 0.0% | 100% |
When a chart is not enough, you should seek care
Charts are not a substitute for assessment. Clinical guidance emphasizes evaluation of early pregnancy complications, particularly when there is pain or bleeding, to rule out conditions like ectopic pregnancy and to provide appropriate support.
Miscarriage risk by day
People want to know;
- What is the chance of miscarriage on this specific day of pregnancy
- What is the chance of miscarriage from today onward, given that the pregnancy has reached this day
Frequently Asked Questions
Key Takeaways (Quick Summary)
- Miscarriage affects ~10–20% of known pregnancies, and many losses happen very early.
- Risk generally declines with gestational age, especially after reassuring ultrasound milestones in certain populations.
- Maternal age is a major population-level risk factor.
- Most miscarriages are not caused by stress or sex, and many are due to chromosomal abnormalities.