No previous miscarriages
1 previous miscarriage
2 previous miscarriages
3 or more previous miscarriages
Estimated Probability of Success:–%
(Probability of pregnancy continuing)
Estimated Daily Miscarriage Risk:–%
Overall Risk for Week :–%
* This tool provides statistical estimates based on general population data. It is not medical advice. Every pregnancy is unique. Please consult your obstetrician for personal risk assessment.
function calculateMiscarriageRate() {
var weekInput = document.getElementById('pregnancyWeek');
var ageInput = document.getElementById('maternalAge');
var historySelect = document.getElementById('historyFactor');
var week = parseInt(weekInput.value);
var age = parseInt(ageInput.value);
var historyMult = parseFloat(historySelect.value);
if (isNaN(week) || week 42) {
alert("Please enter a valid pregnancy week between 3 and 42.");
return;
}
if (isNaN(age) || age 70) {
alert("Please enter a valid maternal age.");
return;
}
// Base Risk Data (Approximation from general statistical meta-analyses)
// Week: Risk %
var baseRisk = 0;
if (week = 14 && week <= 20) baseRisk = 1.0;
else baseRisk = 0.5;
// Age Adjustment Multiplier
var ageMultiplier = 1.0;
if (age = 30 && age = 35 && age = 40 && age = 45) {
ageMultiplier = 5.0; // Very high risk
}
// Calculate Total Risk
var totalRisk = baseRisk * ageMultiplier * historyMult;
// Cap risk at 100% and handle very low probabilities
if (totalRisk > 99) totalRisk = 99;
if (totalRisk 20) totalRisk = 0.5 * ageMultiplier;
var successProbability = 100 – totalRisk;
var dailyRisk = totalRisk / 7; // Rough estimate for daily anxiety management
// Update UI
document.getElementById('results-area').style.display = 'block';
document.getElementById('successRate').innerHTML = successProbability.toFixed(1) + "%";
document.getElementById('weekRisk').innerHTML = totalRisk.toFixed(1) + "%";
document.getElementById('dailyRisk').innerHTML = dailyRisk.toFixed(2) + "%";
document.getElementById('displayWeek').innerHTML = week;
document.getElementById('successBar').style.width = successProbability + "%";
// Color coding based on result
var successEl = document.getElementById('successBar');
if (successProbability > 90) successEl.style.backgroundColor = "#27ae60";
else if (successProbability > 75) successEl.style.backgroundColor = "#f1c40f";
else successEl.style.backgroundColor = "#e74c3c";
}
Understanding Miscarriage Rates by Week
The fear of pregnancy loss is a common concern for expectant parents. While statistics cannot predict the outcome of an individual pregnancy, understanding how miscarriage rates decrease over time can provide reassurance. The "danger zone" is typically considered the first trimester, specifically the first 6 to 8 weeks.
How Pregnancy Week Affects Risk
The risk of miscarriage drops significantly as a pregnancy progresses. Once a heartbeat is detected via ultrasound (usually around week 6 to 7), the risk of pregnancy loss drops dramatically to under 10% for women under 35. By the end of the first trimester (week 12), the risk for the general population usually falls below 2%.
This calculator estimates probability based on three primary factors:
Gestational Age: The further along the pregnancy, the lower the risk.
Maternal Age: Chromosomal abnormalities, which are the most common cause of early miscarriage, occur more frequently as maternal age increases.
History: Recurrent pregnancy loss can statistically increase the likelihood of future losses, though many women with a history of miscarriage go on to have healthy pregnancies.
Statistical Breakdown by Week
Here is a general breakdown of miscarriage risks for a healthy woman under the age of 35:
Gestational Week
Approximate Risk
Chance of Continuation
Week 3-4
20-30%
70-80%
Week 5
~18-20%
~80%
Week 6-7
~10-12%
~90%
Week 8-9
~4-6%
~95%
Week 10-13
< 3%
> 97%
Week 14-20
< 1%
> 99%
The Impact of Maternal Age
Age is one of the strongest predictors of pregnancy outcomes. As egg quality naturally declines over time, the rate of chromosomal anomalies increases.
Under 35: Baseline risk (typically 10-15% overall).
Age 35-39: Risk increases to approximately 20-25% overall.
Age 40-44: Risk increases to approximately 40-50%.
Age 45+: Risk can be higher than 70%.
Frequently Asked Questions
When does the risk of miscarriage drop the most?
The most significant drop usually occurs after a heartbeat is confirmed, typically around week 7 or 8. Another major milestone is reaching the second trimester (week 13), where the risk becomes minimal.
What is a "Chemical Pregnancy"?
A chemical pregnancy is a very early miscarriage that happens shortly after implantation, usually before the fifth week. Many occur before a woman even knows she is pregnant, but sensitive home pregnancy tests now detect these earlier than before.
Does stress cause miscarriage?
Everyday stress, work, or exercise typically do not cause miscarriages. The vast majority of early pregnancy losses are due to chromosomal abnormalities that prevent the embryo from developing properly.