Conjoined twins

Twins who are joined together at birth.

An extremely rare condition in which twins are physically joined at birth. The majority of conjoined twins are female; more than half are stillborn. Conjoined twins were once called Siamese twins, after Chang and Eng Bunker, the famous 19th century conjoined twins from then Siam (present-day Thailand). Twins may be joined at the head, chest, abdomen, or hip. Some of them share vital organs such as the heart or liver. In others, only umbilical blood vessels connect them. The care of conjoined twins and questions about separating them are extremely complicated. Many ethical dilemmas arise, such as when and if it is ever appropriate to sacrifice one twin so that the other can survive.

Identical twins who are united bodily but are possessed of separate personalities. Their frequency is not known, but it has been estimated that throughout the world, six or more conjoined twins are born every year who are capable of separation. The earliest case on record is that of the “Biddendon Maids’ who were born in England in 1100. The ‘Scottish Brothers’ lived for 28 years at the court of James III of Scotland. Perhaps the most famous conjoined twins, however, were Chang and Eng, who were born of Chinese parents in Siam in 1811. It was they who were responsible for the introduction of the term, ‘Siamese twins’, which still remains the popular name for ‘conjoined twins’. They were joined together at the lower end of the chest bone, and achieved fame by being shown in Barnum’s circus in the United States. They subsequently married English sisters and settled as farmers in North Carolina. They died in 1874.

Identical twins become physically connected due to a failure to divide during their growth from a solitary fertilized egg. Conjoined twins are alternatively referred to as Siamese twins.