Parents of twins will tell you that they are twice as nice, or double the trouble, depending on the sort of day they are having!
There’s an estimated 400,000 twins in Australia, which is around 2% of the population. In the 20 years from 1989 to 2009, the number of multiple births in Australia increased by 27%. The majority of multiple births is twins, with the remaining being triplets and higher multiples such as quadruplets, quintuplets and so on.
Experts say the growing number of multiple births is largely due to the increased use of fertility drugs and assisted reproduction technology, the delay in child-bearing and the growing number of older mothers. Approximately one third of all sets of twins are identical. Identical twins occur when the fertilised egg divides into two then it’s still a tiny collection of cells. The two halves then develop into two babies with the exact same genetic information.
The other two thirds of twins are non-identical, or fraternal. They’re the result of two separate eggs fertilised by two separate sperm. They can be either the same sex, or different sexes.
Here are some interesting facts about twins you might not have known!
1. You can tell identical twins apart by their belly buttons
Our belly buttons are scars that are created when the umbilical cord detaches after birth, so they aren’t caused by genetics. You can also tell identical twins apart by their fingerprints, just like everyone else.
2. Twins can have different fathers or be different races
It is possible for fraternal twins to have different dads, if a woman has sex with more than one man during ovulation. Sperm from each man fertilises an egg resulting in twins. If the men are from different racial backgrounds, the babies will be too. The phenomenon is quite rare, however.
3. You can be pregnant with two babies at once who aren’t twins
These two babies can share a womb at the same time, and may even be born on the same day, but they’re not twins. It’s an incredibly rare condition called superfetation that happens when a pregnant woman continues menstruation and a second embryo forms. The foetus conceived last is usually born prematurely, while the foetus conceived first is carried to term. But sometimes they can be born on the same day.
4. Some twins have their own language
It might just sound like babble to everyone else, but researchers have found that up to 40 per cent of twins create their own private language that only they can understand. The term is called cryptophasia, and describes how twin babies use each other to learn vocabulary.
5. Some identical twins are mirror images of one another
If a fertilised egg splits later in the process than usual, some of the appearance and other traits of an identical twin can be a mirror image of the other. For example, one may be left-handed and the other right handed. There have been extreme cases where mirror image twins’ organs have been reversed.
6. Twins help their mothers live longer
A study of birth records between 1800 and 1970 by researchers from the University of Utah found that mothers who have given birth to twins tend to live longer than mothers who haven’t.
7. Twins begin bonding in the womb
We’ve all seen adorable pictures of cute baby twins holding hands and snuggling. They actually start interacting with each other in the womb as early as 14 weeks gestation.
8. When identical twins marry identical twins and have kids…
The wonders of DNA and genetics mean that if a pair of identical male twins marry a pair of identical female twins, their kids will legally be cousins but genetically be full siblings. Children are considered to be genetic siblings if the chromosomes they receive are derived from the same pool. Because the genetic pool of identical twins is identical, the two sets of parents produce children from identical pools.
9. Tall women are more likely to have twins
Researchers from the Long Island Jewish Medical Centre found that taller women have more of the insulin-like growth factor protein that increases the chance of ovulation. The more protein she has, the greater the chance she will have twins.
10. Twins really do run in the family
The “twin gene” you hear about isn’t a myth. Women who have fraternal twins in their families inherit a gene that causes multiple eggs to be released during ovulation. Women who are fraternal twins themselves are twice as likely to give birth to twins.