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!
