Estimate the statistical risk of pregnancy loss based on age and gestational week.
0
1
2
3 or more
Based on your inputs, the estimated statistical risk of miscarriage at this stage is:
Probability of a successful pregnancy:
Medical Disclaimer: This calculator provides estimates based on general statistical data and clinical studies. It is not a medical diagnosis. Every pregnancy is unique, and factors like smoking, BMI, and underlying health conditions are not included in this simple model. Always consult your obstetrician for personalized medical advice.
Understanding Miscarriage Risks
Miscarriage is defined as the spontaneous loss of a pregnancy before the 20th week. While the topic is often difficult to discuss, it is statistically common, occurring in approximately 10% to 20% of known pregnancies. Understanding the factors that influence these numbers can help provide perspective during the early stages of gestation.
Key Factors Influencing Probability
The two most significant variables in determining miscarriage risk are maternal age and how far along the pregnancy has progressed.
Maternal Age: As age increases, the risk of chromosomal abnormalities—the most common cause of early loss—also increases.
Gestational Progress: Once a fetal heartbeat is detected (usually around week 6-8), the probability of miscarriage drops significantly. By the time a pregnancy reaches the second trimester (week 13), the risk falls to less than 1% for most women.
Obstetric History: Having one prior miscarriage typically does not significantly increase the risk for the next pregnancy. However, two or more consecutive losses may indicate underlying factors that require medical investigation.
Statistical Risk by Maternal Age
Age Group
Average Risk (Early Pregnancy)
Under 35
~12% – 15%
35 – 39
~20% – 25%
40 – 44
~35% – 50%
45 and older
Over 65%
Why Do Most Miscarriages Happen?
Most early pregnancy losses (about 50% to 70%) are the result of random chromosomal abnormalities. These are not inherited from the parents but occur by chance during the division and growth of the embryo. Other factors can include hormonal imbalances, uterine abnormalities, or chronic illnesses like uncontrolled diabetes.
When to Seek Medical Attention
While some spotting can be normal in early pregnancy, you should contact your healthcare provider immediately if you experience heavy bleeding, severe abdominal pain, or cramping. This calculator is designed for informational purposes and should not replace professional prenatal care.
function calculateMiscarriageRisk() {
var age = parseFloat(document.getElementById('maternalAge').value);
var week = parseFloat(document.getElementById('gestationalWeek').value);
var history = parseInt(document.getElementById('priorLosses').value);
var resultBox = document.getElementById('resultBox');
var riskSpan = document.getElementById('riskPercentage');
var survivalSpan = document.getElementById('survivalPercentage');
if (isNaN(age) || isNaN(week) || age < 1 || week < 3) {
alert("Please enter a valid age and pregnancy week (minimum 3 weeks).");
return;
}
// Base risk based on age
var baseRisk = 0;
if (age = 30 && age = 35 && age = 40 && age < 45) {
baseRisk = 42.0;
} else {
baseRisk = 65.0;
}
// Week adjustment (Survival curve approximation)
// Risk drops as weeks increase
var weekMultiplier = 1.0;
if (week = 10 && week 12 && week 15) {
weekMultiplier = 0.04;
}
// History adjustment
var historyMultiplier = 1.0;
if (history == 1) {
historyMultiplier = 1.1;
} else if (history == 2) {
historyMultiplier = 1.35;
} else if (history >= 3) {
historyMultiplier = 1.6;
}
// Calculate final estimated risk
var finalRisk = baseRisk * weekMultiplier * historyMultiplier;
// Boundary checks
if (finalRisk > 95) finalRisk = 95;
if (finalRisk < 0.2) finalRisk = 0.2;
var survivalChance = 100 – finalRisk;
// Display Results
riskSpan.innerText = finalRisk.toFixed(1) + "%";
survivalSpan.innerText = survivalChance.toFixed(1) + "%";
resultBox.style.display = 'block';
// Smooth scroll to result
resultBox.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}