It is a phenomenon that is incredibly rare, occurring in only 1 in 100,000 live births.
Yet, when it does happen, it often comes with a poor prognosis.
As many as 60% of conjoined twins do not usually make it past the first few days of life.
It is a subject that often comes with many questions.
How are conjoined twins created?
What can be done for conjoined twins who continue to survive after birth and how do doctors
go about separating them?
Also, what is the quality of life like for those who do not undergo the surgery?
In the normal process of identical or monozygotic twin creation, the fertilized egg, otherwise
known as a zygote, splits into two inside the mother.
This happens very early on, often before the woman even realizes that she is pregnant.
In the case of conjoined twins, however, the splitting of the zygote pauses before the
process is complete.
Development then continues as normal, forming two fused embryos that will eventually result
in connected infants.
So, can it also occur in fraternal or dizygotic twins?
As you may already know, creation of fraternal twins occur when two separate eggs are fertilized
by two different sperm.
As with identical twins, fraternal twins do not share 100% of the same genes.
Instead, fraternal twins are more like regular siblings, sharing 50% of their genes and they
may or may not resemble one another.
While identical twins are almost always born the same sex, fraternal twins can vary.
Boy-girl twins are the most common kind of dizygotic twins, occurring in 50% of cases.
Girl-girl twins are the second most common and boy-boy twins are the least common.
Only in very rare instances of chromosomal conditions can monozygotic twins consist of
different sexes.
While nonidentical twins can’t become conjoined, they can become something called chimeras.
This occurs when fraternal twins fuse together early in development.
The word, “chimeras,” originally derived from Greek mythology as a beast with a lion’s
head, a goat's body and a serpent’s tail.
Real chimeras, however, are not quite this dramatic.
The scientific definition relates to a genetic phenomenon within organisms that occur when
an individual develops from two or more zygotes with distinct genotypes.
Thus, this does not result in two separate connected people like with conjoined twins
but, rather, a single person consisting of genes from a mix of both twins.
This would be like combining two of your siblings into one person.
In essence, you could be your own twin brother or sister.
If that isn’t confusing enough, consider the interesting fact that, although uncommon,
it is technically possible for fraternal twins to have different fathers.
This happens when two eggs are fertilized, each from the sperm of a different man.
Theoretically, it is possible that these twins could then fuse together, creating a person
with chimerism who has two biological fathers.
It is easy to imagine that this could lead to some very confusing family dynamics.
In the case of chimerism though, it is incredibly rare with only 30-100 cases known to this
day.
Returning to the topic of conjoined twins, you might wonder what happens with those who
survive and how do doctors separate them.
Separating conjoined twins is a highly risky procedure and many doctors will not do it
unless it is absolutely necessary for the quality of life of the impacted individuals.
It is typically based on a case by case basis and really depends on what part of the body
the twins are connected and whether they can survive separation.
Obviously, if they share too many vital organs, separation is more difficult.
If twins share a heart, for instance, successful surgery becomes impossible.
If, however, they only share a liver and GI tract, surgery is a more realistic option.
Obviously, if twins have separate sets of organs, chances for successful surgery and
survival are greater.
The rarest type of conjoined twins has to do with being connected at the head.
The name for this is craniopagus twins.
Separation for this type depends upon whether the twins share a brain or if they are connected
at the skull that acts as a barrier between two distinct brains.
In this case, it is possible to cut through the skull to separate them.
Modern medicine makes separation for conjoined twins much easier and more benefit from successful
surgery.
This is incredible when considering that past generations had no hope for it.
Historically, connected twins who survived infancy had to remain conjoined throughout
their entire lives.
An example of this comes from a famous set of twins known as Eng and Chang Bunker who
were connected at the stomach.
They were brothers born in Thailand in 1811.
During this time, Thailand was called “Siam,” thus coined the term “Siamese twins.”
That name is no longer valid today though since it has a negative stigma associated
with it.
The fact that Eng and Chang were boys is especially rare because, for reasons doctors do not yet
fully understand, female conjoined twins are more likely to survive than males.
As many as 70-75% that live tend to be female.
Thus, the brothers were truly exceptional.
The boys lived out their lives pretty normally for the most part and even wound up marrying
two different women.
They often had to take turns staying in the home of each wife because the two women didn’t
want to sleep in the same bed with one other.
The men also ended up having many children.
Chang had 10 kids and Eng had 11.
Towards the end of their lives, however, Chang became an alcoholic and Eng wanted to be separated
from him because he didn’t want to have to carry around Chang’s lifeless body upon
death.
In the end, Eng only lived a few hours after Chang’s death.
The cause of his passing is unclear though some believed he died out of shock from seeing
his dead brother.
Because Eng and Chang were only connected by the liver, doctors believe they could have
easily been separated had they been alive today.
At the time, however, such surgery would have been fatal, resulting in excessive blood loss,
which would have most likely killed them both.
So why separate conjoined twins?
Well, for one, conjoined twins that live after birth are more susceptible to greater health
problems and complications.
Their positioning may also leave them more uncomfortable, having to bend their backs
and contort their bodies in unnatural ways to accommodate their connection.
Successful separation also allows twins to live fully independent, autonomous lifestyles
apart from one another and to be able to freely make decisions for themselves without having
to consult the sibling they’re connected to.
In some cases, however, not separating them might be the better option for an improved
quality of life.
One such case involves that of Abby and Brittany Hensel, twins with two different heads who
share a single body.
In a 2011 documentary about these girls, doctors explained that their quality of life would
be worse if they were to be separated because each girl would only have one arm and one
leg and barely be able to function normally without the other.
The documentary depicted Abby and Brittany’s life as being as close to normal as possible.
They attended high school in a small town where everyone knew them and weren’t so
shocked by their appearance.
In school, the girls managed to have many friends and be treated like two, distinct
individuals despite being connected at the body.
Their teachers were interviewed saying that one was very outgoing while the other was
more reserved.
The girls even received two different driver’s licenses and are perfectly capable of driving
a car like a normal person.
In their case, each twin controls her side of the body and, together, their movements
coordinate with one another.
Talk about teamwork!
Though they claim not to be able to feel the other’s side of the body, however, they
will appear to be so synchronized with one another that one will unconsciously scratch
a mosquito bite on the arm of the other.
Doctors are puzzled by this and believe that there must be a strong, psychological bond
that connects the two for these kinds of harmonized movements.
They admit though that sleeping is often made difficult since positioning can be a challenge.
When asked if they would have liked to be separated, Abby and Brittany said no.
They explained when interviewed that they did not know any other way of being and they
greatly enjoy each other’s company.
Today, the girls work as fifth grade teachers though they are given one salary and treated
as one employee.
This annoys them greatly because they have two different degrees and two different perspectives
on how to teach.
Life for them can often be frustrating with the constant confusion of outsiders on whether
to treat the twins separately or as one.
Still, the two are inspirational for others since they do not let people bring them down
or prevent them from living a fulfilling life.
In this way, the girls can be viewed as figures of unity and strength.
If you’re planning to start a family someday, perhaps you’re wondering what the odds are
of having conjoined twins or even twins in general?
Well, as mentioned at the beginning, your chances of having conjoined twins are roughly
around 1 in 100,000, which makes it highly unlikely.
With those numbers, half of those conjoined twins tend to be stillborn.
This means that your chances of having surviving conjoined twins are about 1 in 200,000 – highly,
highly unlikely.
Though, if you do manage to beat the odds, perhaps you should consider buying a ticket
and trying your chances with playing the lottery.
Now maybe you’re curious about the odds of having twins in general, not conjoined.
Ultrasound technicians can usually tell very early on whether you’re carrying twins.
Whether the twins are monozygotic or dizygotic, however, can be very difficult to determine.
Usually fraternal twins can be identified if the babies are different sexes or have
different blood types.
Your odds of having twins in general are influenced by a wide variety of different factors.
Many of these include whether you’re a woman over the age of 30, using fertility treatments,
overweight, taller than average, or have a family history of twins.
Overall, the rate for identical twins is pretty much constant across all regions while fraternal
twin production has been suggested to be highly affected by ethnicity and location.
The reasoning behind this is mostly indeterminate.
But, overall, those of African ethnicity are most likely to produce fraternal twins, while
Asians are the least likely.
By location, there can be much differentiation in this.
In 2003, statistics in the United States showed that the twin rates for black Americans were
higher at around 17 per 1,000 pregnancies.
For Caucasian Americans, this number was roughly 15.
This may not seem like a major difference at first glance but, when compared to other
countries, the gap widens.
In the same year, the twinning rates in Denmark, Greece and the Netherlands were around 20
per 1,000 births while Nigeria had them beat with a whopping twinning rate of 40 per 1,000.
That’s double the amount!
Still, even within Nigeria, there were variations of twins found between different regions.
Western and Eastern Nigeria carried the highest rates with 33 to 67 twins per 1,000 births
while this number was lower in Northern Nigeria with only 19.
Again, the reasoning behind this is unclear.
If you were a conjoined twin would you want to be separated?
Or do you think having the constant source of companionship might be kind of appealing?
Let us know in the comments!
Also, be sure to check out our other video The World's Craziest ER Stories!
Thanks for watching, and, as always, don’t forget to like, share, and subscribe.
See you next time!