Useful information on when women more likely to have twins, triplets or multiples with advice on multiple pregnancy and birth.
- The average length of pregnancy is 36 weeks for twins and 33-34 weeks for triplets.
- Identical twins are formed from a single egg which splits after fertilisation.
- Non-identical (fraternal) twins are formed from two fertilised eggs. The only sure-fire way to know if yours are identical or fraternal (apart from them being boy/girl twins) is from a DNA test.
- Twins are on the increase: older mothers and fertility treatment increase the likelihood of a double hit!
- Nigerian women have the highest rate of twinning in the world.
- Even identical twins don't share identical fingerprints. Each of your children is truly unique.
If you wait to have children until you're in your 30s or beyond, you face a greater chance than younger women of having twins or more. As you age, you naturally produce more ovulation-stimulating hormones, which could trigger your ovaries to release several eggs each month.
Larger, taller women are 25 to 30 percent more likely to have twins.
Heredity is an important factor too. Non-identical twins tend to run in families, usually on the mother's side, but not always. If twins run in your mother's family, you're more likely to have a set yourself, but identical twins do not tend to run in families.