1. Siamese Twins / Conjoined Twins
Bellaflores, Marc Gideon L.
DMD2D

2. What are Siamese Twins?

Conjoined twins are identical Instead of creating two
twins that have not split separate embryos, the two
properly after fertilization, embryos will remain
they share a body and may attached, causing the babies
share vital organs. to grow into one another.

Identical twins are created
from a single fertilized egg.

If the egg does not separate
within 12 days, it will not split
completely.

3. History of Conjoined Twins
A popular term for conjoined
twins is “Siamese twins”
The term comes from Eng and
Chang Bunker who were
famous conjoined twins born
in Siam in 1811.
The term “Siamese twins” is no
longer considered appropriate
because they aren’t limited to
any racial or ethnic group.

4. Are Conjoined Twins Common?

Conjoined twins are not Are more likely to occur in
a common occurrence. India or Africa than in
China or the United

Only about one set of
States.
conjoined twins are born
every 400,000 births, but Conjoined twins are more
only once in every often female than male,
200,000 LIVE births. at a ratio of 3:1 or 70%.

5. Types of Conjoined Twins

Thoraco-omphalopagus (28% of cases):[7] Two bodies fused from the upper
chest to the lower chest. These twins usually share a heart, and may also
share the liver or part of the digestive system.[8]

Thoracopagus (18.5%):[7] Two bodies fused from the upper thorax to lower
belly. The heart is always involved in these cases.[8]

Omphalopagus (10%):[7] Two bodies fused at the lower chest. Unlike
thoracopagus, the heart is never involved in these cases; however, the twins
often share a liver, digestive system, diaphragm and other organs.[8]

Parasitic twins (10%):[7] Twins that are asymmetrically conjoined, resulting
in one twin that is small, less formed, and dependent on the larger twin for
survival.

Craniopagus (6%):[7] Fused skulls, but separate bodies. These twins can be
conjoined at the back of the head, the front of the head, or the side of the
head, but not on the face or the base of the skull.[8]

7. Separation
Separation of conjoined twins is
usually performed at a very
young age.
In some cases the brain or the
heart must be separated in
order to provide each twin
with vital organs.
To date, about 200 separations
have been performed.

8. When to Separate

In the past, surgery was delayed until twins were 6-12
months old so that they could become stronger.

Since there are now life-support systems and
diagnostic tools are more sophisticated, earlier
separation is more common.

Immediate separation is needed when one twin is
stillborn.

Separation while twins are too young to realize that
they are joined is thought to help their psychological
recovery.

9. Dental Correlation
• When conjoined twins are not separated all
administered drugs are calculated on a total-
weight basis, with half being delivered to
each twin
• But most conjoined twins now a days are
separated so a normal dental procedure is
given to them

10. Classification
• I classify Conjoined twins into Mendelian genetics
because sometimes Some twins fraternal or dizygotic
twins only are the result of hyperovulation, a female
tendency to release multiple eggs during ovulation. If
two or three or more eggs are fertilized and implant,
the result is twins or multiples. Hyperovulation can be a
genetic tendency, so if a mother has the gene for it, her
daughter might also. In that sense, it can be said that
twins run in the family, but on the mother's side only.
Fathers don't ovulate, so they don't impact twinning in
this scenario.