How siamese twins form
Jun 30, 2003
Twins are a blessing, especially in Uganda, where they give parents an elevated social status. However, there is a rare form of identical twins that occurs in one out of every 75,000 to 100,000 births, or one in 200 deliveries of identical twins
By Juliet Nsiima
Twins are a blessing, especially in Uganda, where they give parents an elevated social status. However, there is a rare form of identical twins that occurs in one out of every 75,000 to 100,000 births, or one in 200 deliveries of identical twins. These are conjoined/siamese twins.
In history, conjoined twins were considered ‘monsters’ and ‘freaks’ and were either killed at birth or hidden away from society. In Greek mythology, the birth of conjoined twins was thought to be a result of the gods’ fury at their mother for having intercourse with animals.
However, medicine has proved that conjoined twins originate from a single fertilised egg. This means that they are identical and same-sex twins.
The developing zygote starts to split into identical twins within the first two weeks after conception, but then stops before completion, leaving a partially separated egg that continues to mature into a conjoined foetus.
In normal cases, identical twins can be completely separated between four to 16 weeks. Fraternal twins can never be conjoined because two eggs are fertilised and the zygotes form two placentas in the womb.
“The birth of two sets of conjoined twins in Uganda is recorded annually,†says Dr. Sam Mutumba, a veteran pediatrician of 19 years.
“Sixty percent of normal identical twins are male. However, 70% of conjoined twins are female. Most of the conjoined twins that are still-born are males. Most females are born alive. There is no explanation for this.â€
According to statistics, approximately 40-60% of these births are delivered stillborn with 35% surviving just one day. The overall survival rate of conjoined twins is somewhere between 5-25% and historical records over the past 500 years detail about 600 surviving sets of conjoined twins with more than 70% of those surviving pairs resulting in female twins.
“Early last year (May, 2002), the conjoined twin girls commonly known as the Lango twins, were born. They are actually Sudanese refugees. Their names are Christine and Louise (or Loyce). They were born to Margaret Athai and Gordon Onziga.
“Some years back, we had the Bagisu twin girls, Nalule A and B. The Lango twins were delivered through the vagina, unlike the Nalule twins, who were delivered through caesarean section. They are all thoraopagus twins,†says Dr. Mutumba.
This means they were born facing each other and sharing a chest wall.
The Lango twins survived because they did not share a pelicaliam –– a sac that covers the heart, unlike the Nalule twins in which it was totally fused.
They both shared a heart, but the Lango twins’ heart could be divided, whereby the weaker twin had three heart chambers and the stronger twin had the usual four chambers. The weaker Nalule twins’ heart was underdeveloped and was feeding off the stronger one.
“The birth of these children can be extremely traumatic for the parents. The girls were brought to Mulago Hospital in November (2002) because they needed to be separated urgently. They were already six months old and it is imperative that conjoined twins be separated before they are a year old, so as to ensure the survival of both or one of them.
These operations also ensure that they develop different personalities like ordinary identical twins.
“Fortunately, both (of the Lango) children are alive, but were given up for adoption to a US family. The weaker Nalule twin unfortunately had to be sacrificed or else she would have strained the heart of the stronger one and eventually killed them both,†Mutumba says.
“At times it is better not to separate conjoined twins. The separation of the Iranian twins in Singapore is very risky. Personally, I would not undertake that operation. The twins share a cranium and a brain.â€
In ordinary neural operations, any slight damage to the brain causes a stroke to the patient. The doctors are going to separate their brain into two, meaning one of the twins will be lost or severely paralysed.
If one twin dies, probably the stronger twin will follow suit because she will be too weak physically, intellectually and emotionally to live on her own. They do not have separate personalities, since they have shared the same brain for 30 years.
There will not be a quiet twin and an outspoken twin. Their mood swings and intelligence are the same. The brain controls intellect, emotions and impulses like smell and touch.
Secondly, if they both survive, they will have to live together for the rest of their lives. They will have to stay in the same house, go to the same work places or companies. They are already qualified lawyers. Even still, if one twin dies, the other will die shortly.
“However, the Iranian twins have a right and a choice to be separated,†Mutumba says on the contrary. “Their discomfort is too much because of the psycho-social pressure on them. People shun them when they are in public and they may have shown affection to the opposite sex and been rejected,†Mutumba concludes.
According to CNN.com and twinsource.com, more cases of conjoined twins occur in Africa, Asia and South America than in Europe and North America.
“This is because pre-natal clinical examination is an unwritten law in the developed world, unlike the underdeveloped world,†explains Dr. Mutumba.
“Twins can be detected early, like if the mother has a huge abdomen and large amounts of amblyopic fluids to accommodate them. Conjoined twins can be detected through ultrasound scans and the mother is usually advised to terminate her pregnancy because most of these children do not even survive childbirth.
While there are dozens of types of conjoined twins, they are usually classified in seven categories. They are more broadly categorized as displaying either equal or symmetrical forms or unequal and asymmetrical forms. Some twins can be categorised in more than one category.
Thoraopagus:
These are the most common form of conjoined twins, occurring in between 35-40% of all cases. The twins share part of the chest wall, possibly including the heart.
Omphalopagus:
These twins are united from the waist to the lower breastbone, accounting for about 34% of conjoined cases. For instance, the famous Siamese twins, Eng and Chang Bunker (1811-74) of United States. They fathered 22 children between themselves.
Pygopagus:
The twins are likely positioned back-to-back and usually have a posterior connection at the rump. They share the anus. This occurs in almost 20% of documented cases. An example is the African-American twins Millie and Christine McKoy (1851-1912). They were circus singers known as the Two-Headed Nightingale.
Ischiopagus:
About 6% of all conjoined twins have this condition, with the twins joined by the coccyx (lowest part of the backbone) and the sacrum, the part of the backbone immediately above the coccyx). An example is Mary and Eliza Chulkhurst in Kent, England, wealthy conjoined twins (at hips or buttocks) who bequeathed their fortune to the Church. Annual celebrations were held in England for centuries where cakes displayed their images.
Craniopagus:
These twins are joined at the cranium (the top of the head or skull). Occurring in just 2% of all conjoined twin cases, this is a very difficult type of twin to separate, although advances in medicine have led to more than 35 successful separations. Two female craniopagus twins were successfully separated in Lithuania in 1989, for example. Currently, there are the 30-year old Iranian twins that are about to be separated in Singapore.
Cephalopagus:
The twins share the anterior union of the upper half of the body with two faces on opposite sides of a conjoined head. This case is extremely rare. The heart is sometimes involved.
Dicephalus:
Twins share one body with two separate heads and necks. Examples are Abigail and Brittany Hensel of USA; the Tocci Brothers of Scotland, Masha and Dasha Krivoshyapovy (1950 to present) of former USSR.
Source: Craig Sanders, twinstuff.com, CNN.com, twinsource.com
Twins are a blessing, especially in Uganda, where they give parents an elevated social status. However, there is a rare form of identical twins that occurs in one out of every 75,000 to 100,000 births, or one in 200 deliveries of identical twins. These are conjoined/siamese twins.
In history, conjoined twins were considered ‘monsters’ and ‘freaks’ and were either killed at birth or hidden away from society. In Greek mythology, the birth of conjoined twins was thought to be a result of the gods’ fury at their mother for having intercourse with animals.
However, medicine has proved that conjoined twins originate from a single fertilised egg. This means that they are identical and same-sex twins.
The developing zygote starts to split into identical twins within the first two weeks after conception, but then stops before completion, leaving a partially separated egg that continues to mature into a conjoined foetus.
In normal cases, identical twins can be completely separated between four to 16 weeks. Fraternal twins can never be conjoined because two eggs are fertilised and the zygotes form two placentas in the womb.
“The birth of two sets of conjoined twins in Uganda is recorded annually,†says Dr. Sam Mutumba, a veteran pediatrician of 19 years.
“Sixty percent of normal identical twins are male. However, 70% of conjoined twins are female. Most of the conjoined twins that are still-born are males. Most females are born alive. There is no explanation for this.â€
According to statistics, approximately 40-60% of these births are delivered stillborn with 35% surviving just one day. The overall survival rate of conjoined twins is somewhere between 5-25% and historical records over the past 500 years detail about 600 surviving sets of conjoined twins with more than 70% of those surviving pairs resulting in female twins.
“Early last year (May, 2002), the conjoined twin girls commonly known as the Lango twins, were born. They are actually Sudanese refugees. Their names are Christine and Louise (or Loyce). They were born to Margaret Athai and Gordon Onziga.
“Some years back, we had the Bagisu twin girls, Nalule A and B. The Lango twins were delivered through the vagina, unlike the Nalule twins, who were delivered through caesarean section. They are all thoraopagus twins,†says Dr. Mutumba.
This means they were born facing each other and sharing a chest wall.
The Lango twins survived because they did not share a pelicaliam –– a sac that covers the heart, unlike the Nalule twins in which it was totally fused.
They both shared a heart, but the Lango twins’ heart could be divided, whereby the weaker twin had three heart chambers and the stronger twin had the usual four chambers. The weaker Nalule twins’ heart was underdeveloped and was feeding off the stronger one.
“The birth of these children can be extremely traumatic for the parents. The girls were brought to Mulago Hospital in November (2002) because they needed to be separated urgently. They were already six months old and it is imperative that conjoined twins be separated before they are a year old, so as to ensure the survival of both or one of them.
These operations also ensure that they develop different personalities like ordinary identical twins.
“Fortunately, both (of the Lango) children are alive, but were given up for adoption to a US family. The weaker Nalule twin unfortunately had to be sacrificed or else she would have strained the heart of the stronger one and eventually killed them both,†Mutumba says.
“At times it is better not to separate conjoined twins. The separation of the Iranian twins in Singapore is very risky. Personally, I would not undertake that operation. The twins share a cranium and a brain.â€
In ordinary neural operations, any slight damage to the brain causes a stroke to the patient. The doctors are going to separate their brain into two, meaning one of the twins will be lost or severely paralysed.
If one twin dies, probably the stronger twin will follow suit because she will be too weak physically, intellectually and emotionally to live on her own. They do not have separate personalities, since they have shared the same brain for 30 years.
There will not be a quiet twin and an outspoken twin. Their mood swings and intelligence are the same. The brain controls intellect, emotions and impulses like smell and touch.
Secondly, if they both survive, they will have to live together for the rest of their lives. They will have to stay in the same house, go to the same work places or companies. They are already qualified lawyers. Even still, if one twin dies, the other will die shortly.
“However, the Iranian twins have a right and a choice to be separated,†Mutumba says on the contrary. “Their discomfort is too much because of the psycho-social pressure on them. People shun them when they are in public and they may have shown affection to the opposite sex and been rejected,†Mutumba concludes.
According to CNN.com and twinsource.com, more cases of conjoined twins occur in Africa, Asia and South America than in Europe and North America.
“This is because pre-natal clinical examination is an unwritten law in the developed world, unlike the underdeveloped world,†explains Dr. Mutumba.
“Twins can be detected early, like if the mother has a huge abdomen and large amounts of amblyopic fluids to accommodate them. Conjoined twins can be detected through ultrasound scans and the mother is usually advised to terminate her pregnancy because most of these children do not even survive childbirth.
While there are dozens of types of conjoined twins, they are usually classified in seven categories. They are more broadly categorized as displaying either equal or symmetrical forms or unequal and asymmetrical forms. Some twins can be categorised in more than one category.
Thoraopagus:
These are the most common form of conjoined twins, occurring in between 35-40% of all cases. The twins share part of the chest wall, possibly including the heart.
Omphalopagus:
These twins are united from the waist to the lower breastbone, accounting for about 34% of conjoined cases. For instance, the famous Siamese twins, Eng and Chang Bunker (1811-74) of United States. They fathered 22 children between themselves.
Pygopagus:
The twins are likely positioned back-to-back and usually have a posterior connection at the rump. They share the anus. This occurs in almost 20% of documented cases. An example is the African-American twins Millie and Christine McKoy (1851-1912). They were circus singers known as the Two-Headed Nightingale.
Ischiopagus:
About 6% of all conjoined twins have this condition, with the twins joined by the coccyx (lowest part of the backbone) and the sacrum, the part of the backbone immediately above the coccyx). An example is Mary and Eliza Chulkhurst in Kent, England, wealthy conjoined twins (at hips or buttocks) who bequeathed their fortune to the Church. Annual celebrations were held in England for centuries where cakes displayed their images.
Craniopagus:
These twins are joined at the cranium (the top of the head or skull). Occurring in just 2% of all conjoined twin cases, this is a very difficult type of twin to separate, although advances in medicine have led to more than 35 successful separations. Two female craniopagus twins were successfully separated in Lithuania in 1989, for example. Currently, there are the 30-year old Iranian twins that are about to be separated in Singapore.
Cephalopagus:
The twins share the anterior union of the upper half of the body with two faces on opposite sides of a conjoined head. This case is extremely rare. The heart is sometimes involved.
Dicephalus:
Twins share one body with two separate heads and necks. Examples are Abigail and Brittany Hensel of USA; the Tocci Brothers of Scotland, Masha and Dasha Krivoshyapovy (1950 to present) of former USSR.
Source: Craig Sanders, twinstuff.com, CNN.com, twinsource.com