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					Conjoined Twins

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393

Summary:
Twins are a kind of multiple births, i.e., when a woman gives birth to
more than one baby at the same time. Twins occur when more than one egg
is fertilized or when the same egg is fertilized more than once by one or
two sperm, leading to formation of more than one fetus.


Keywords:
Twins, Identical Twins, Twin Babies, Conjoined Twins


Article Body:
Twins are a kind of multiple births, i.e., when a woman gives birth to
more than one baby at the same time. Twins occur when more than one egg
is fertilized or when the same egg is fertilized more than once by one or
two sperm, leading to formation of more than one fetus.

Conjoined twins are identical twins who are joined together somewhere in
the body. Conjoined twins are monozygotic twins, in the sense that they
share the same zygote. Sometimes, they also share some vital internal
organs. Formation of conjoined twins is believed to be the result of late
twinning. When the twinning occurs more than twelve days after
fertilization of the egg, it may lead to formation of conjoined twins
because the embryo may not split completely. This may be due to genetic
or environmental factors.

Conjoined twins are also known as Siamese twins, named after the famous
conjoined twins, Eng and Chang Bunker from Siam. Conjoined twin births
are very rare, amounting to around one birth in every 1,00,000 births.
Mary and Eliza Chulkhurst, famously referred to as the biddenden maids,
are one of the earliest known set of conjoined twins. The ratio of male
and female sets of conjoined twins was found to be three to one, and they
are found more in certain countries like India or Africa.

Conjoined twins rarely survive because of the complexity of the bodies.
Most of them are stillborn or die within twenty-four hours after birth.
Conjoined twins can be separated surgically if none of the vital organs
are involved. There are different kinds of conjoined twins, depending on
the part of the body where they are joined. These are cephalopagus,
craniopagus, craniothoracopagus, dicephalus, iscopagus, omphalopagus,
parapagus, pygopagus and thoracopagus. There are also some rare kinds of
conjoined twins, such as parasitic twins (where one twin is not
completely formed and depends on the other twin to sustain life), and
fetus in fetu (where one twin’s fetus is present inside the body of the
other twin).

Some people consider separation of conjoined twins as unethical if it
involves death or disability of one of the twins. Conjoined twins, if
they survive, can lead healthy lives. There are instances where conjoined
twins have even married and become parents. The famous Siamese twins,
Chang and Eng Bunker, fathered twenty-one children in thirty-one years.

				
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