Siamese twins (conjoined twins)
"Siamese twins" is a historical term for conjoined twins—identical twins who are born physically connected to each other. While the term is still used colloquially, the medical community and many modern style guides prefer "conjoined twins" as it is more accurate and avoids tying a medical condition to a specific nationality.
1. The Origin of the Term:
The name comes from Chang and Eng Bunker (1811–1874), a famous pair of conjoined brothers born in Siam (now Thailand).
• Life and Fame: They were joined at the sternum by a small band of cartilage. They were brought to the U.S. and exhibited as "The Siamese Twins," eventually becoming a world-famous sensation.
• Legacy: They eventually settled in North Carolina, married sisters, and fathered 21 children between them. They lived to be 62 years old, which remains one of the longest lifespans for unseparated conjoined twins.
2. Why it Happens (Medical Perspective):
Conjoined twins are always identical (monozygotic), meaning they developed from a single fertilized egg. There are two primary theories on how they form:
• Fission (The Splitting Theory): The most common belief is that a single embryo begins to split into two separate individuals but stops before the process is complete (usually 13–15 days after conception).
• Fusion (The Rejoining Theory): A newer theory suggests that two separate embryos may fuse back together in the early stages of development.
3. Common Types of Connection:
Conjoined twins are classified based on where they are joined. The most common types include:
4. Modern Medical Realities:
• Rarity: The condition is extremely rare, occurring in roughly 1 in every 50,000 to 200,000 live births.
• Survival: Approximately 40% of conjoined twins are stillborn, and 35% die within the first 24 hours.
However, medical advances in imaging and surgery have significantly increased the success rate of separation surgeries.
• Separation: Whether twins can be separated depends entirely on which organs they share. For example, twins sharing a single, fused heart are often considered inseparable.
5. Notable Modern Cases:
• Abby and Brittany Hensel: Famous American dicephalic parapagus twins (two heads on one torso) who have separate hearts and stomachs but share most other organs.
• Ronnie and Donnie Galyon: Held the record for the oldest conjoined twins, living to the age of 68 before passing away in 2020.