Chance of Live Birth Calculator

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This calculator combines miscarriage and stillbirth chance to estimate your chance of live birth from today based on maternal age and how far along you are.

General inputs(optional) >
If blank, we use height and weight if entered. Otherwise we use a typical BMI of 26.
Early pregnancy factors (miscarriage)(optional) >
Later pregnancy factors (stillbirth)(optional) >
If you do not want ethnicity included, leave it unselected.
Default is about 1 in 160 (0.625%). You can change this to match your region.
Advanced stillbirth inputs(optional) >
Neonatal survival assumptions(optional) >
Used to estimate “take-home baby” from the live birth estimate.
Used to estimate survival to 28 days from the live birth estimate.

How to use the Chance of Live Birth Calculator

This calculator estimates your chance of a live birth from today. It combines two risks:

  • Miscarriage risk (up to 20 weeks)
  • Stillbirth risk (20 weeks to birth)

  1. Choose how you want to enter timing:

    Gestational age: Use this if you know your weeks and days.

    Due date (EDD): Use this if you know your estimated due date.

  2. Enter maternal age:

    Type your age in years.

  3. If you picked gestational age:

    Enter weeks.

    Enter days (0 to 6). If you are not sure, you can leave days blank.

  4. If you picked due date (EDD):

    Select your due date. The calculator will convert it into gestational age for today.

    If the date works, you will see a line that says your gestational age today.

  5. Optional: add general inputs (applies to both estimates):

    Use General inputs if you want BMI included in both the miscarriage and stillbirth estimates.

    Units: Choose imperial (ft, in, lb) or metric (cm, kg).

    Height and weight: Enter your numbers if you want BMI calculated automatically.

    In imperial mode, height uses feet and inches on the same line.

    BMI override: If you already know your BMI, you can enter it directly.

    If you leave everything blank, the calculator uses a typical BMI value.

  6. Optional: add early pregnancy details (miscarriage factors):

    Open Early pregnancy factors (miscarriage) if you want a more personal miscarriage estimate.

    Ultrasound: Choose yes or no.

    Heartbeat: If you had an ultrasound, pick whether a heartbeat was seen.

    Fetal heart rate: Optional. Enter bpm if you know it.

    Previous miscarriages and live births: Enter counts if any.

    Bleeding: Choose yes or no.

    If you do not want these factors included, you can leave this section closed.

  7. Optional: add later pregnancy details (stillbirth factors):

    Open Later pregnancy factors (stillbirth) if you want to adjust the stillbirth estimate.

    Ethnicity: You can leave it unselected if you do not want it included.

    Baseline stillbirth risk: Leave the default, or change it to match your region.

    You can also open Advanced stillbirth inputs for extra options like IVF, diabetes, hypertension, smoking, and alcohol.

    You can also open Neonatal survival assumptions to estimate:

    Take-home baby: Birth to discharge.

    Survival to 28 days: Birth to day 28.

  8. Click “Calculate >”:

    You will see your estimated chance of live birth.

    You will also see a bar that shows total loss vs live birth.

    Under the bar, you will see miscarriage or stillbirth (combined).

    You will see the breakdown for miscarriage risk and stillbirth risk.

    You will also see take-home baby and survival to 28 days.

Tips:

  • If you had an ultrasound at week 11 or later and no heartbeat was seen, the calculator will stop and show a safety message. Talk with your clinician about next steps.
  • This is a statistical estimate. It cannot predict what will happen in one specific pregnancy.
  • If you want a quick estimate, enter age and timing, then click calculate.

Methodology and sources

This calculator estimates the chance of live birth from today. It combines an estimate of miscarriage risk up to 20 weeks and an estimate of stillbirth risk from 20 weeks to birth. It also shows two optional neonatal survival outputs based on user-set assumptions.

Inputs used

  • Maternal age (years)
  • Pregnancy timing, entered as gestational age (weeks and days) or as an estimated due date (EDD)
  • Optional early pregnancy factors (miscarriage): ultrasound status, heartbeat seen, fetal heart rate, prior miscarriages, prior live births, bleeding, height and weight (BMI)
  • Optional later pregnancy factors (stillbirth): baseline stillbirth risk (%), ethnicity (optional), BMI (from height and weight or override), and optional conditions and exposures
  • Optional neonatal assumptions: early neonatal death risk (%), neonatal death risk to 28 days (%)

How the estimate is calculated

  1. Convert pregnancy timing to gestational age.
    • If you enter gestational age, the calculator uses your weeks and days.
    • If you enter an EDD, the calculator converts it to gestational age for today using a 280-day (40-week) pregnancy length.
  2. Estimate miscarriage risk from today up to 20 weeks.
    • If no heartbeat is selected, the calculator uses a gestational age lookup table (weeks and days) for baseline loss risk.
    • If an ultrasound is marked as done and heartbeat is marked as seen, the calculator uses a lower baseline curve by week, with a small per-day decrease.
    • The baseline pattern matches clinical references that risk generally falls as gestational age increases and is lower after fetal cardiac activity is seen. [1]
  3. Apply miscarriage adjustments using an odds-based multiplier model.
    • The calculator converts risk percent to odds, multiplies by one or more multipliers, then converts back to percent.
    • Maternal age: the calculator maps age to a multiplier using anchor points and linear interpolation. In this implementation, age 35 uses about 1.3, age 40 uses 2.0, age 42 uses 3.0, and age 45 or older uses 4.5. [2]
    • Pregnancy history: prior miscarriages increase the odds (1 prior uses 1.25, 2 uses 1.5, 3 or more uses 2.2). Prior live births reduce the odds (1 prior uses 0.8, 2 or more uses 0.7). [3][4]
    • BMI (if height and weight are entered): BMI under 18.5 uses 1.2; BMI 30 to 34.9 uses 1.3; BMI 35 to 44.9 uses 1.6; BMI 45 or higher uses 1.9. [5]
    • Bleeding: if bleeding is selected, the odds are multiplied by 2.5 without heartbeat, or 1.5 with heartbeat. [1]
    • Fetal heart rate (only if heartbeat is selected): the calculator flags “slow” as under 100 bpm at 6 weeks or earlier, or under 120 bpm at 7 weeks and later. If slow, odds are multiplied by 3.0. If not slow, odds are multiplied by 0.8. [6]
    • The miscarriage risk output is clamped to 0.1% to 99.0%.
  4. Estimate stillbirth risk from 20 weeks to birth using a baseline risk and multipliers.
    • The baseline stillbirth risk is an input. The default is 0.625% (about 1 in 160). This is intended as a general-population starting point and can be changed to match your region. [8][9]
    • If you enter BMI as an override, that value is used. If not, BMI is calculated from height and weight if available. If neither is available, the calculator uses a default BMI of 26.
    • Multipliers in this implementation include maternal age banding, BMI banding, ethnicity (optional), and optional clinical and exposure inputs (ART/IVF, diabetes, hypertension, SLE, APS, smoking, alcohol). These inputs reflect commonly listed stillbirth risk factors in clinical guidance, but the exact multipliers here are simplified for usability. [8]
    • The stillbirth risk output is clamped to 0% to 20%.
    • Important: this stillbirth estimate is not adjusted by current gestational week. It is treated as a single risk from 20 weeks to birth.
  5. Combine miscarriage and stillbirth to estimate live birth chance.
    • Live birth chance (from today) is calculated as: (1 – miscarriage risk) x (1 – stillbirth risk).
    • Total loss chance (combined miscarriage or stillbirth) is calculated as: 1 – live birth chance.
    • This assumes the two risks are independent. That is a simplification.
  6. Estimate take-home baby and survival to 28 days (optional).
    • These outputs apply user-set neonatal death assumptions to the live birth estimate.
    • Take-home baby chance = live birth chance x (1 – early neonatal death risk).
    • Survival to 28 days chance = live birth chance x (1 – neonatal death risk to 28 days).
    • If the 28-day risk is set lower than the early neonatal risk, the calculator raises it to match the early neonatal value.
    • Neonatal mortality is commonly reported as deaths under 28 days. [10]

Guardrails in the calculator

  • If gestational age is 20 weeks or later, the miscarriage component is treated as 0% because “spontaneous abortion” is typically defined before 20 weeks in US clinical references. Definitions can vary. [1]
  • If ultrasound is marked as done, gestational age is 11 weeks or later, and heartbeat is marked as not seen, the calculator stops and shows a safety message instead of a percentage. Diagnosis of non-viability relies on ultrasound criteria and clinical assessment. [7]

Limitations

  • This is a population-based estimate. It cannot diagnose miscarriage or predict an individual outcome.
  • Dating error can materially change the estimate, especially in early weeks.
  • The miscarriage baseline tables and multipliers are simplified for usability and are not a validated clinical prediction model.
  • The stillbirth model uses a single risk from 20 weeks to birth and does not vary by gestational week.
  • The stillbirth multipliers are simplified and do not represent a single published regression model.
  • The neonatal outputs are based on user-set assumptions and are not adjusted for gestational age, birthweight, or NICU factors.
  • The combined formula assumes independence between miscarriage and stillbirth risks.

Sources

Support if you have experienced a loss

Reading about miscarriage, stillbirth, or infant loss can be difficult. If you have experienced a loss, you do not have to use this calculator or read the statistics. You may find it more helpful to talk with your care team or a support organization.

In the United States, groups such as:

offer information and bereavement support. If you are elsewhere, your local health service or a pregnancy and baby loss charity may be able to guide you to support in your region.

Medical disclaimer

The information and calculators on this site are educational tools only. They provide statistical estimates based on published research and the details you enter.

They cannot diagnose, predict what will happen for you, or replace personalized advice from a licensed health care professional who knows your full history. Always talk with your doctor, midwife, or other qualified clinician before making decisions about your health, fertility, or pregnancy.

Never ignore, avoid, or delay seeking professional medical advice because of something you read here or a result you see in a calculator. If you think you may be having a medical emergency, call 911 in the United States or your local emergency number.