Stillbirth risk calculator

Stillbirth is the death of a fetus at or after twenty weeks of gestation, and families, midwives, educators, and product teams often need a transparent percentage that combines how far the pregnancy has already come, the mother's age, and a short list of well-studied clinical flags. This stillbirth risk calculator estimates remaining stillbirth probability from gestational age between twenty and forty-two weeks, maternal age, and selected optional risk factors—previous stillbirth, pre-existing diabetes, hypertension, smoking, obesity, fetal growth restriction, and multiple pregnancy—using a remaining-risk table, age relative risks, and odds-adjusted factor multipliers.

What remaining stillbirth risk means and how gestational age, age, and factors combine

Stillbirth in this calculator follows the conventional United States vital-statistics threshold: fetal death at or after twenty completed weeks of gestation, rather than the twenty-four-week cut used in some other reporting systems. The quantity returned is a remaining-risk percentage. Given that the pregnancy has already reached the stated gestational age, the engine estimates stillbirth probability through the rest of pregnancy after maternal age and selected flags are applied.

That is a different question from the week-specific stillbirth rate among deliveries that happen to occur at that week, which is dominated at twenty to twenty-three weeks by the fact that many of those births are themselves stillbirths. Remaining risk is the counselling-style figure people search for when they type stillbirth risk calculator.

Baseline remaining stillbirths per thousand ongoing pregnancies sit near recent United States incidence of about six per thousand at week twenty and then decline toward term, with a modest uptick at forty-one and forty-two weeks that reflects the well-described rise in weekly stillbirth hazard after the due date when birth has not yet occurred.

Maternal age is converted to a relative risk with a nadir in the mid-twenties, a mild rise through the early thirties, and a steeper rise after thirty-five and again after forty, following the pattern reported by Reddy and colleagues. Optional flags for previous stillbirth, pre-existing diabetes, chronic or pregnancy hypertension, smoking, obesity at a body-mass index of thirty or more, fetal growth restriction, and multiple pregnancy multiply the odds by published Flenady-style relative risks rather than adding raw percentages, so stacked factors saturate below one hundred percent instead of overshooting.

Gestational age must lie between twenty and forty-two weeks inclusive; values outside that window are rejected because both the remaining-risk table and the stillbirth definition itself are undefined there.

How to read the percentage, where the calculator belongs, and what it does not decide

Risk bands are remaining-risk strata, not a personal prognosis. Low remaining risk is under two stillbirths per thousand ongoing pregnancies, the usual teaching band near term with no stacked factors. Moderate remaining risk is two up to five per thousand, which covers much of mid-pregnancy at baseline.

High remaining risk is five up to ten per thousand, typical of early remaining-risk at twenty weeks or a modest cluster of flags later on. Very high remaining risk is ten or more per thousand and usually means a previous stillbirth, fetal growth restriction, or several multipliers have been combined; the odds model still keeps the percentage below one hundred. Those bands are historical-style educational cuts, not delivery-timing rules.

They do not replace kick-counts, cardiotocography, growth scans, Doppler studies, induction counselling, or a clinician's view of comorbidities this table never captures—cholestasis, antiphospholipid syndrome, substance use beyond the smoking flag, or reduced fetal movements on the day of the visit. Use the calculator for education, exam keys, research coding of obstetric rows, and product prototypes that need a deterministic stillbirth-risk step before handing off to licensed systems.

Neighbouring tools such as a due-date engine, a pregnancy-week calculator, or a pregnancy weight-gain band answer different search intents and should keep their own landings rather than being overloaded here.