Twin probability calculator — full estimate

Complete seven questions for an educational estimate of spontaneous twin probability. The six numerical weights are conservative heuristics, treatment effects are excluded, and the model is not clinically validated. Your answers stay in this browser tab.

Question 1 / 7Current estimate1.3%

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Spontaneous fraternal-twin rates generally rise with age, then level off in recent population data.

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Source

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References

  1. CDC NCHS — Twin Birth Rates: United States, 2024
  2. Beemsterboer et al. (2006) — maternal age and multifollicular development
  3. ASRM (2022) — multiple gestation associated with infertility therapy
  4. CDC — ART National Summary
  5. Smits & Monden (2011) — twinning across the developing world
  6. Updated GWAS meta-analysis of spontaneous dizygotic twinning (2024)
  7. Reddy et al. (2005) — maternal height, BMI and twinning