Success of surgery depends on where the twins are conjoined

THE NEWS that the conjoined twins born six weeks ago are being prepared for surgery is good news for the boys’ parents and extended family.

The success of the surgical procedure depends on where the twins are joined and to what extent they share vital organs such as the brain, liver and heart.

Great Ormond Street Hospital, where the surgery will take place later this year, has a superb reputation for this highly specialised work.

Conjoined twins occur when a single fertilised egg splits into two embryos. However, if this split is delayed for more than 12 days post-conception, the embryos do not fully divide and the twins may share body parts. Like all monozygotic (identical) twins, conjoined twins are always the same gender. About 70 per cent of conjoined twins are female.

The birth of conjoined twins is a rare event, occurring in between one in 50,000 and one in 100,000 births. About 28 per cent of conjoined twins are joined at both the chest and abdomen.

Conjoined twins became known as Siamese twins following the birth of Chang and Eng Bunker who were born in Siam (now Thailand) in the early 1800s.

They travelled the world as celebrities before eventually settling in the US. The first set of conjoined twins was recorded in Constantinople in AD945, with the first surgical separation carried out in 1953.

The pioneering work of Prof Lewis Spitz and Prof Ed Kiely, which started over 25 years ago, has made Great Ormond Street Hospital one of the few centres in the world with the expertise to carry out this technically demanding surgery.

In 2003, the team at the hospital successfully separated Zainag and Jannat Rahman who shared a liver in a way that allowed the surgeons to give both an independent existence.