Estimating survival probability based on clinical data
Male
Female
Yes
No / Unknown
Estimated Survival Rate
Understanding Preemie Survival Rates
The survival rate of premature infants has significantly improved over the last decade due to advancements in neonatal intensive care (NICU). This calculator uses statistical data typically derived from the NICHD (National Institute of Child Health and Human Development) outcomes to provide an estimate.
Key Factors Explained
Gestational Age: The single most critical factor. Every day spent in the womb increases the maturity of the lungs and brain.
Antenatal Steroids: These are injections given to the mother before birth to help speed up the baby's lung and organ development.
Infant Sex: Historically, female preemies often show a slightly higher survival rate and lower morbidity compared to males at the same gestational age.
Birth Weight: A higher birth weight for a specific gestational age generally indicates better growth and higher resilience.
Medical Disclaimer: This tool provides estimates based on historical population data and averages. It does not predict the outcome for any specific individual. Each case is unique, and you should always consult with your neonatologist or medical professional for clinical guidance.
Examples of Survival Statistics
Gestational Age
Approx. Survival Rate
23 Weeks
20% – 35%
24 Weeks
50% – 65%
26 Weeks
80% – 90%
28 Weeks
90% – 95%
32 Weeks
> 95%
function calculateSurvival() {
var weeks = parseInt(document.getElementById('weeksInput').value);
var days = parseInt(document.getElementById('daysInput').value) || 0;
var weight = parseInt(document.getElementById('weightInput').value);
var sex = document.getElementById('sexInput').value;
var steroids = document.getElementById('steroidInput').value;
var resultArea = document.getElementById('resultArea');
var survivalPercentage = document.getElementById('survivalPercentage');
var survivalDetails = document.getElementById('survivalDetails');
if (isNaN(weeks) || weeks < 22) {
alert("Please enter a gestational age of at least 22 weeks.");
return;
}
if (isNaN(weight) || weight = 31 && weeks = 34) baseRate = 99;
// Day increment (linear interpolation to next week)
var nextWeekRate = baseRate;
if (weeks === 22) nextWeekRate = 30;
else if (weeks === 23) nextWeekRate = 55;
else if (weeks === 24) nextWeekRate = 72;
else if (weeks === 25) nextWeekRate = 84;
else if (weeks === 26) nextWeekRate = 89;
else if (weeks === 27) nextWeekRate = 92;
else if (weeks === 28) nextWeekRate = 94;
else if (weeks === 29) nextWeekRate = 95;
else if (weeks >= 30) nextWeekRate = 99;
var dayBoost = ((nextWeekRate – baseRate) / 7) * days;
var currentRate = baseRate + dayBoost;
// Adjust for Sex
if (sex === 'female') {
currentRate += 4;
}
// Adjust for Steroids
if (steroids === 'yes') {
currentRate += 12;
} else {
currentRate -= 5;
}
// Weight correction (Average weight for 24w is ~600g, 28w ~1000g)
// Simple penalty for very low weight relative to age
var expectedWeight = (weeks – 14) * 110;
if (weight expectedWeight * 1.2) {
currentRate += 2;
}
// Cap rates
if (currentRate > 99) currentRate = 99;
if (currentRate = 22) currentRate = 5;
if (weeks < 22) currentRate = 1;
// Display
resultArea.style.display = "block";
survivalPercentage.innerText = Math.round(currentRate) + "%";
if (currentRate < 40) {
resultArea.style.backgroundColor = "#fff5f5";
survivalPercentage.style.color = "#e53e3e";
} else if (currentRate < 80) {
resultArea.style.backgroundColor = "#fffaf0";
survivalPercentage.style.color = "#dd6b20";
} else {
resultArea.style.backgroundColor = "#f0fff4";
survivalPercentage.style.color = "#38a169";
}
survivalDetails.innerHTML = "Based on " + weeks + " weeks and " + days + " days, " + (sex === 'female' ? "a female" : "a male") + " infant weighing " + weight + "g has an estimated survival probability of approximately " + Math.round(currentRate) + "%. Antenatal steroids " + (steroids === 'yes' ? "significantly improved" : "would have improved") + " these odds.";
}
Frequently Asked Questions
What is the "limit of viability"? The limit of viability is generally considered to be between 22 and 24 weeks of gestation. Below 22 weeks, the lungs are usually not developed enough to sustain life even with mechanical ventilation.
Do these statistics include long-term health? No, this calculator only estimates the probability of survival to discharge from the NICU. It does not account for potential long-term complications like CP, vision issues, or developmental delays.