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Characteristics of Siamese Twins

Babies born conjoined twins were formerly referred to as Siamese Twins. Now, the proper medical and socially responsible term is conjoined twins. This condition is very rare, according to the Mayo Clinic, occurring more in Africa and India than any other nations in the world. Conjoined twins can share organs or limbs. In some extremely uncommon cases, twins are conjoined in an asymmetrical fashion where one of the babies is smaller and not completely formed.

  1. Symptoms

    • When a woman is pregnant with twins that are conjoined, there are no concrete physical tell-tale symptoms which indicate the condition. Similar to traditional twin pregnancies, the pregnant woman may experience more rapid uterine growth. Women carrying multiples also experience increased nausea, vomiting and fatigue in the early stages of their pregnancies. A sonogram is the only reliable method of determining if a woman is carrying conjoined twins.

    Thoracopagus

    • Twins that are joined at the chest are called thoracopagus. These twins share a heart and in some cases may share an upper intestine and one liver.

    Pygopagus

    • When twins are joined at the base of the spine, they are called pygopagus. In some cases, pygopagus twins may share genital organs, the lower gastrointestinal tract and urinary organs.

    Omphalopagus

    • Twins that are joined at the navel are called omphalopagus. Some of the organs that these twins may share include the lower portion of the small intestine, the colon and the liver. Omphalopagus twins do not share a heart.

    Craniopagus

    • When twins share a skull and are joined at the head, they are called craniopagus. In some of these cases twins share brain tissue. It is also possible for craniopagus twins to share the cerebral cortex portion of their brain. This is significant because the cerebral cortex plays an integral part in language, perception and memory.

    Causes

    • Normal twins are formed when a fertilized egg splits in two and grows into two separate fetuses. In the case of conjoined twins, the egg does not completely separate, resulting in babies that are conjoined. Where the egg does and does not split determines where the twins are joined. There are also scientific theories which suggest that conjoined twins occur when two embryos fuse together early on in their development process. It is unknown what causes either of these scenarios.

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