Siamese Twins Conjoined Twins Explained

I recently seen a T.V. show about conjoined twins and was rather interested and wanted to know more about the condition as far as how it happens and what different types of conjoined twins there are. I found the information so interesting I wanted to share my new found knowledge with you.

Conjoined twins are always identical twins who develop with a single placenta from a single fertilized ovum. They are always the same sex and race. Conjoined twins are more often then not females over males at a ratio of 3:1. Conjoined twins occurs as often as once in every 40,000 births but only once in every 200,000 live births. Conjoined twins are more likely to be born to a mother in India or Africa than they are to be born to a mother in the United States or China.

Conjoined twins may be caused by a many number of factors such as being influence by environmental conditions or genetics. Conjoined twins is a failure of the twins to separate after the 13th day after fertilization of the egg. There has never been a documented case of conjoined triplets or quadruplets.

There are several types of conjoined twins and they are usually classified by how they are joined. Here are several basic ways and names that doctors and scientist have classified the different types of conjoined twins into.

1.)Conjoined twins that never involve heart or umbilicus

*Craniopagus: Which means the twins are conjoined at the cranium (head) only. This happens in about 2% of all conjoined twins.

*Pygopagus. Which means posterior union of the rump (butt). This happens in about 19% of all conjoined twins. They have separate hearts but may share one spinal cord. There is one anus, two rectums and four legs and arms.

2.)Conjoined twins that always involve the Umbilicus (Midline Conjunctions)

*Thoracopagus: Which means an anterior union (face to face) of the upper half of the trunk through the chest wall from the thorax all the way down to the umbilicus. This is the most common form of conjoined twins and happens in about 35%. This always involves sharing the heart.

*Cephalopagus: Which means an anterior union of the upper half of the body with two faces on opposite sides of a conjoined head. The twins will be joined from the top of the head down to the umbilicus with separate lower abdomen and pelvis. This form of conjoined twins is extremely rare. The heart is sometimes involved.
*Parapagus (sometimes called diprosopus): Is the lateral union of the lower half, extending variable distances upward and happens in about 5% of all conjoined twins. The union of the upper body varies and may also include sharing of the heart sometimes.

*Ischopagus: Which means an anterior union of the lower half of the body. This happens in about 6% of all conjoined twins. The heart is not involved.

*Omphalopagus: Which means an anterior union of the midtrunk, usually at the abdomen but the connection can range from the thorax down to the umbilicus. Omphalopagus twins may share a liver, gastrointestinal or genitourinary functions, but rarely share a heart. There are four leg and arms and also two pelvises. This happens in about 30% of conjoined twins.

3.)Rare forms of conjoined twins, having different patterns.

*Parasitic twins: Which means an asymmetrical conjoined twins, one twin being small, less formed, and dependent upon the other.

*Fetus in fetu: Situation in which an imperfect fetus is contained completely within the body of its sibling.

As you can see there are many types and differences in each case of conjoined twins. After the conjoined twins are born parents and doctors can decided to surgically separate the twins. An emergency separation may be needed if one of the twins dies or if one twin develops a life threatening condition that will affect the life of the other twin. More often though the separation surgery is an elective surgery done around two to four months of age. The survival rate of the elective separation is much higher at 80% than the emergency separation that only carries a 29% survival rate.

There are many factors that go into making the decision to separate the conjoined twins. Factors such as are the twins healthy enough to withstand and survive the separation? Do the twins share any vital organs and if so what are they? What are the realistic odds of survival for both twin if they are separated? What types of reconstructive surgery will be needed for each twin after the separation? What issues will the twins face if they are not separated? What issues will they face if they are separated? Answers to these and many other questions help doctors and parents make an educated decision on what is the best route to take for each case of twins.

If separation is not possible or if parents choose not to separate their conjoined twins comfort and care is provided as on going care for the conjoined twins. There are many documented cases of conjoined twins who are not separated who live happy, fulfilling and rewarding lives though out the world.