Abrachiocephaly means being born without arms (also
known as abrachia) and a head (also known as
acephaly). The condition is considered a variant of
acephaly. It is a much more rare condition than
anencephaly, which is when the fetus is born without
a major portion of the brain, skull, and cap. A fetus is
a developing human that is inside the mother from the
end of the 8th week to birth. The abrachiocephalic
fetus is a parasite attached to a fetus that is
otherwise intact. A parasite is any organism that lives
in or on another living being, gains an advantage by
doing so, but causes disadvantage to the being it is
living on.
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A fetus with abrachiocephaly  is also missing a heart. The heart of the twin provides
circulation to the fetus with abrachiocephaly.  The neck is connected to the normal twin
and needs to be surgically separated at birth. Once this separation is complete, the fetus
with abrachiocephaly cannot live. Abrachiocephaly is also known as abrachiocephalia
and acephalobrachia.

Abrachiocephaly comes from the Greek word "a" meaning "without," the Greek word
"brachion" meaning "arm," and the Greek word "kephale" meaning "head." Put the words
together and you have "without arm(s) (and) head."
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