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Twin Probability

Calculate Twin Probability instantly with the exact formula and a worked example.

Twin Probability

Mother's ageyears
Conception (1 = all births in the population, 2 = IVF / assisted reproductive technology)
Twins per 1,000 births
42.8
Source: NCHS Data Brief No. 351 (CDC, 2019) — twins per 1,000 births by mother's age, US, 2018; the data include pregnancies after fertility treatmentThe twin rate rises with the mother's age (partly due to IVF in older women); natural fraternal twins are more common with a family history on the mother's sideShare of deliveries with twins ≈ r / (2000 − r), where r is twins per 1,000 births; triplets and higher are ignored. These are population statistics, not a personal predictionCalculate Twin Probability instantly with the exact formula and a worked example.
Age group (NCHS 2018)
35–39 years
Share of deliveries with twins (approx.)
2.19%
About 1 twin delivery in
46
Share of babies born as twins
4.28%
Same rate in 2014
48.6
All ages, US 2018
32.6

More about: Twin Probability

What it calculates

The “Twin Probability” calculator computes Twins per 1,000 births from 2 parameters: mother's age (years), conception (1 = all births in the population, 2 = ivf / assisted reproductive technology).

A lab calculation in biology and molecular biology.

Example calculation

With parameters Mother's age = 35 years, Conception (1 = all births in the population, 2 = IVF / assisted reproductive technology) = 1 the result is 42.8 (Source: NCHS Data Brief No. 351 (CDC, 2019) — twins per 1,000 births by mother's age, US, 2018; the data include pregnancies after fertility treatment).

How to use

  1. Enter mother's age and conception (1 = all births in the population, 2 = ivf / assisted reproductive technology) — each field above is adjustable with a slider.
  2. Twins per 1,000 births is calculated automatically as you type.
  3. Check the worked example below to see the formula applied to real numbers.
  4. Copy the result or bookmark this calculator.

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FAQ

How is Twin Probability calculated?
The Twin Probability calculator computes Twins per 1,000 births from mother's age, conception (1 = all births in the population, 2 = ivf / assisted reproductive technology). Enter your values above and the exact formula is applied instantly; a worked example with real numbers is shown below.
Is the Twin Probability calculator free?
Yes. It is completely free, needs no signup, runs entirely in your browser, and sends no data to any server.

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