Secret languages. Higher levels of morning sickness. Telepathy?
Welcome to the wonderful, fascinating and (sometimes mind-blowing) world of twins!
While twinning rates in Australia have remained constant over the past decade, overall, one in 80 births in Australia is born a twin. Of that number, 30 percent are identical with the other 70 percent fraternal.
“Identical twins are a miracle. There’s no hereditary incidence of identical twins but non-identical (or fraternal) can be hereditary and there’s definitely an increased chance if you have them in your family,” Lynette Walker from the Australian Twin Registry told The Huffington Post Australia.
Miracles aside, there's a whole bunch of other fun and interesting facts about twins -- some of which we've rounded up below.
The chance of having twins again once you’ve already had them increases
This is not a drill. If you’ve had fraternal twins once, it’s likely you’ll fall pregnant with twins again. This is to do with some women having the natural ability to ovulate more than others. Hyperovulation -- as it’s called is when two or more eggs can descend during ovulation instead of just one.
The rate of twin births in Australia has dropped
According to the Australian Twin Registry, the number of twins born in 2014 (4, 381) was 3.7 percent lower than the number recorded in 2013 (4, 550).
When IVF first started the number of twin births increased due to the multiple embryo transfer involved which significantly increases the chances of twins.
“Now they have the technology that allows them to implant just one egg instead of multiple,” Walker said.
Mirror image twins are an actual thing
Mirror image twins occur when the fertilised egg splits later, sometimes a week after conception resulting in the twins developing reverse asymmetric features. This means one twin may be left-handed while the other right-handed.
Science is yet to prove the telepathic connection between twins, but the anecdotal evidence is fascinating
“Scientists will argue there are two things at play when twins are able to feel each other’s pain or know what the other is thinking; genetics and environment,” Walker said.
For example, identical twins are a 100 percent genetic match so it’s not surprising that they would have similar personalities and reactions to things. While non-identical it would be argued, if they are particularly close and have spent all their time together it is not unusual for them to be so intuitive with each other.
Libby Nixon recalls her dad, who is a mirror twin telling stories from his childhood about how intuitive he was with his twin brother.
“They would often fool teachers at school pretending to be the other twin. Dad said they would only have to glance at each other to know what the other boy was thinking and they got up to a lot of mischief. They had two really interesting moments of twin telepathy as adults. When one was having a heart operation, the other experienced excruciating chest pain -- so bad that he went to hospital thinking he was having a heart attack -- he wasn't. My dad later found out his twin was having a heart operation at the time,” Nixon told HuffPost Australia.
Mums of twins can expect more morning sickness
As well as growing two, not one, small humans inside your tummy unfortunately mothers of twins can experience more morning sickness (or all day sickness!) than mothers of singletons. This is due to the sudden increase in hormones. But it gets better. While every woman is different, morning sickness usually improves by the fourth month.
It is possible for twins to have different dads
But how? Two eggs from the same mother get fertilised by two different fathers -- within the same ovulation period. During this time there is a five-day fertility window, which means if you’ve got multiple sexual partners and aren’t using protection, fraternal twins with two different dads is quite frankly, possible.