Estimate your chance of a twin pregnancy from the factors that actually move the numbers — age, family history, IVF and more.
Older eggs are more likely to release twice (hyperovulation).
Hyperovulation gene passes through the mother’s line.
Base rate
In the US, about 1 in 40 pregnancies (2.5%) are twins. Identical twins (~0.3%) are random — unaffected by most factors here. This tool mainly models fraternal twins.