HEALTH
REPORT - Conjoined Twins
By Nancy Steinbach
This is Phoebe Zimmerman with the VOA Special English
Health Report.
Some estimates say that one in as many as eighty-thousand
of all births results in two babies joined together. Conjoined
twins（联体婴儿）happen about once out of every two-hundred births
of identical twins（同卵双胞胎）.
Some twins develop from two separate eggs（卵细胞）that
are fertilized（受精）at the same time. These
babies are called fraternal twins（异卵双生）.
One can be a girl and the other a boy.
Other twins develop from a single egg. These are called
identical twins. Identical twins result when a fertilized egg divides
into two.
Sometimes the division begins but is not completed.
This produces twins who are physically linked. Medical experts say genetic
and environmental influences are involved in the development of conjoined
twins.
Recent separations have taken place in Britain, Singapore,
Italy, Australia and the United States. These included an operation
where doctors at the Children's Medical Center in Dallas, Texas, separated
two Egyptian boys joined at the head.
Conjoined twins may be linked only by a thin piece
of tissue（组织）. Or they may be attached
at the chest or other part of the body. Sometimes they share a heart
or other internal organ.
In the past, conjoined twins were called Siamese
twins（暹罗双胎）. This was because the first well-known twins were
born in Siam（暹罗，泰国的旧称）, the country now
called Thailand. Chang and Eng were born in eighteen-eleven. A twelve-centimeter-long
ligament（韧带）near their breastbones（胸骨）connected
them. Chang and Eng grew up, married and had a total of twenty-one children.
The two men died in eighteen-seventy-four.
Historically, the survival rate for conjoined babies
has been between five and twenty-five percent. But medical progress
has increased those chances.
Today, most conjoined twins are found during examinations
before they are born. Some are easier to separate than others.
The book "Entwined Lives" by Nancy Segal
says doctors have performed about two-hundred operations to separate
conjoined twins. Ninety percent have taken place since nineteen-fifty.
The book says most of the operations resulted in the survival of at
least one of the babies.
One Web site where you can learn more about conjoined
twins is twinstuff-dot-com.
This VOA Special English Health Report was written
by Nancy Steinbach. This is Phoebe Zimmermann.
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