Estimate the risk of stillbirth in your pregnancy based on maternal, medical, and pregnancy risk factors
| Risk per 1,000 | Category | Clinical implication |
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Founder & CEO, Toolraxy
Faiq Ur Rahman is a web designer, digital product developer, and founder of Toolraxy, a growing platform of web-based calculators and utility tools. He specializes in building structured, user-friendly tools focused on health, finance, productivity, and everyday problem-solving.
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This stillbirth risk calculator estimates the chance of stillbirth in a current pregnancy based on maternal, medical, and pregnancy factors. It’s built for expectant parents and clinicians who want a quick, numbers-based look at risk without digging through published cohort studies. The tool uses baseline risk figures by race and ethnicity, then adjusts for factors like age, BMI, diabetes, chronic hypertension, smoking, plurality, and obstetric history. A 38-year-old woman with pre-gestational diabetes and a BMI of 34 will get a different estimate than a 25-year-old with none of those factors. That’s the point. The output is a risk estimate per 1,000 births, a relative risk multiplier, and a plain-language risk category. It’s not a diagnosis. It’s a starting point for a more informed conversation with a provider.
Pick a preset from the dropdown if you want a starting point. Options include average-risk pregnancy, advanced maternal age, obesity with gestational diabetes, previous stillbirth, and a high-risk profile.
Enter your age in years. The tool accepts ages 15 through 55.
Choose your race or ethnicity. This sets the baseline risk because stillbirth rates differ by population group.
Set gestational age in weeks. Anything from 20 to 43 weeks works.
Select plurality. Singleton, twins, or triplets and higher.
Choose your parity: no previous births, one to two, or three or more.
Enter pre-pregnancy BMI. The field accepts decimals, so 23.4 is fine.
Answer the medical history questions: chronic hypertension, diabetes type, preeclampsia, smoking status, previous stillbirth, prior preterm birth, IUGR, substance use, and ART use.
Tap Calculate. The result updates automatically as you change inputs, but the button forces a recalculation if you want one.
The tool uses a multiplicative risk model. It starts with a baseline stillbirth rate per 1,000 births for your racial or ethnic group, applies a gestational age modifier, then multiplies by a relative risk factor built from your individual inputs.
Formula: Risk per 1,000 = Baseline × GA modifier × Relative Risk
The baseline values range from 4.4 per 1,000 for Asian-American pregnancies to 10.5 per 1,000 for African-American pregnancies. The gestational age modifier adjusts risk based on how much pregnancy remains. Earlier gestations carry a higher modifier because more time remains at risk. At 28 weeks the modifier is 1.30; at 39 weeks it drops to 0.90; at 42 weeks and beyond it’s 0.60.
The relative risk multiplier is where the individual factors come in. Each factor has a published odds ratio or relative risk. The tool multiplies them together in log space, which is a standard epidemiological approach. Age 40 or older adds a 1.9× multiplier. Pre-gestational diabetes adds 2.5×. Previous stillbirth adds 3.0×. IUGR adds 2.8×. Twins add 2.5×. These multiply, so a pregnancy with three moderate risk factors can end up with a substantial combined relative risk.
The final risk per 1,000 is clamped between 0.3 and 300. That prevents extreme outliers from producing nonsensical results. The percentage shown is simply the per-1,000 figure divided by 10.
Let’s walk through a 36-year-old woman, white, 37 weeks pregnant with a singleton. She’s had one previous birth. Her BMI is 31. She has gestational diabetes and smoked during the first trimester but quit. No chronic hypertension, no preeclampsia, no previous stillbirth, no IUGR, no substance use, no ART.
Start with baseline: 4.8 per 1,000 for white race.
Gestational age modifier at 37 weeks: 1.00.
Now the relative risk multipliers. Age 36 falls in the 35–39 bracket, so that’s 1.5×. BMI 31 falls in the 30–34.9 bracket, so 1.4×. Gestational diabetes adds 1.3×. Quit smoking adds 1.2×. Parity of 1–2 doesn’t add anything; nulliparous would add 1.2× but she’s not nulliparous.
Multiply those together: 1.5 × 1.4 × 1.3 × 1.2 = 3.276.
Baseline × GA modifier × RR = 4.8 × 1.00 × 3.276 = 15.72 per 1,000.
That’s about 1.57% risk. The tool would categorize this as moderate risk, because it falls in the 10–19.9 per 1,000 band. The relative risk display would show 3.28×. The verdict banner would suggest discussing increased surveillance with a provider — growth scans, fetal movement awareness, that sort of thing.
About 6 in 1,000 births in the United States end in stillbirth. That’s roughly 21,000 per year. The rate varies by race, with African-American pregnancies at about 10.5 per 1,000 and Asian-American pregnancies at about 4.4 per 1,000.
Miscarriage is pregnancy loss before 20 weeks. Stillbirth is loss at or after 20 weeks. That’s the only clinical distinction. The causes overlap, but stillbirth is much less common than miscarriage.
No calculator captures every factor. This tool uses published relative risks for major demographic and medical factors, but it can’t account for placental pathology, cord accidents, or genetic abnormalities. It’s an estimate, not a prediction.
Yes. A BMI of 30 to 34.9 adds a 1.4× multiplier. BMI 35 or higher adds 1.7×. Underweight (BMI under 18.5) also adds risk, at 1.3×. The relationship between BMI and stillbirth is U-shaped in some studies, but this tool treats it as a stepwise increase.
Current smoking adds a 1.8× multiplier. Quitting during pregnancy reduces that to 1.2×. The earlier you quit, the lower the residual risk. Smoking one to nine cigarettes a day still increases odds compared with not smoking at all.
No. Recurrence risk is elevated, roughly 2 to 10 times baseline depending on the cause but most people who have a stillbirth go on to have a healthy pregnancy. The calculator applies a 3.0× multiplier for previous stillbirth, which reflects the midpoint of published estimates.
The tool’s GA modifier peaks at 1.30 for gestations under 28 weeks. That’s because more pregnancy remains, not because early gestations are inherently more dangerous per week. Actual stillbirth rates per week are highest at extreme preterm gestations and decline toward term.
Pre-gestational diabetes adds a 2.5× multiplier. Gestational diabetes adds 1.3×. The risk depends on blood sugar control. Poorly controlled diabetes is more dangerous than well-controlled diabetes. The calculator can’t distinguish between the two.
Preeclampsia adds a 1.8× multiplier. The relative risk is highest when preeclampsia develops preterm. At 26 weeks, one study found an 86× relative risk compared with pregnancies without preeclampsia. At 34 weeks it was still over 7×.
Yes. Twins add a 2.5× multiplier and triplets add 3.5×. Monochorionic twins carry additional risk because of shared placental circulation. The calculator doesn’t separate monochorionic from dichorionic twins.
IUGR stands for intrauterine growth restriction. It means the fetus is smaller than expected for gestational age. The calculator applies a 2.8× multiplier when IUGR is selected. If you don’t know whether IUGR is present, leave it at “no” or “unknown.”
Technically yes, but the results won’t mean anything. The calculator is designed for current pregnancies. Gestational age and plurality are required inputs. Without a current pregnancy, those fields don’t apply.
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