HEALTH · MISCARRIAGE RISK
Miscarriage Risk Calculator
Estimate early pregnancy loss risk by maternal age, prior pregnancy losses, and whether a fetal heartbeat has been confirmed on ultrasound.
These are population-level estimates based on published research. Individual risk depends on many factors not captured here. This tool is for educational purposes only — not a medical assessment.
About This Calculator
Miscarriage — pregnancy loss before 20 weeks — affects roughly 10–20% of known pregnancies, but population-level risk varies considerably with maternal age, prior loss history, and whether a fetal heartbeat has been detected on ultrasound. This calculator combines those three factors into a single adjusted risk estimate based on published epidemiological data.
How It Works
Select your maternal age group and enter the number of prior pregnancy losses. The base rate for your age group is multiplied by a prior-loss factor (none, one, two, or three or more losses). If a fetal heartbeat has been confirmed on ultrasound, the adjusted risk is capped at approximately 3%, reflecting the dramatic risk reduction that follows heartbeat detection. The result is expressed as a percentage with a risk tier (Low / Moderate / Elevated / High).
The Formula
adjustedRisk = min(baseRisk × lossMultiplier, 3.0%) if heartbeat confirmed adjustedRisk = baseRisk × lossMultiplier otherwise
- baseRisk
- age-stratified baseline miscarriage rate (%)
- lossMultiplier
- prior loss adjustment factor (1.0 – 2.0)
- 3.0%
- post-heartbeat risk cap based on published data
Frequently Asked Questions
- What does the heartbeat toggle do?
- When a fetal heartbeat is confirmed on ultrasound, it is a strong prognostic indicator that the pregnancy is developing normally. The adjusted risk is capped at approximately 3%, regardless of age group or prior losses, reflecting the fact that risk drops sharply once cardiac activity is seen.
- Are these numbers accurate for my individual situation?
- No. These are population-level estimates derived from epidemiological research. Individual risk is influenced by many factors not captured here — genetic conditions, anatomy, thyroid function, clotting disorders, and more. This calculator is for educational awareness only, not personal medical prediction.
- What counts as a prior pregnancy loss?
- Any pregnancy that ended before 20 weeks gestation, whether naturally (miscarriage) or through a recognized pregnancy that did not continue. Some research also includes biochemical pregnancies (very early losses detected only by hCG). If you are unsure, discuss with your healthcare provider.
- Why is risk much higher at 40 and beyond?
- The primary driver is chromosomal aneuploidy — errors in chromosome number during egg development — which increases substantially with maternal age. At 40–44, roughly 38% of recognized pregnancies end in miscarriage; at 45+, this rises to approximately 55%.