Don't Pass Without Typing Amen- Parasitic Twin

Parasitic twins occur when a twin embryo begins developing in utero, but the pair does not fully separate, and one embryo maintains dominant development at the expense of its twin.

Unlike conjoined twins, one ceases development during gestation and is vestigial to a mostly fully formed, otherwise healthy individual twin. The undeveloped twin is defined as parasitic, rather than conjoined, because it is incompletely formed or wholly dependent on the body functions of the complete fetus. The independent twin is called the autosite.

A baby boy has been born with his parasitic twin's head and arms hanging down from his chest.

Both newborns share the same liver and a large portion of their blood but have a seperate heart and lungs.

The yet-to-be named baby is fully formed but his undeveloped brother is missing his genitals and legs.  

Doctors believe it is likely they will be able to detach the pair but the operation will be risky.

But to the shock of medics, who helped her deliver the baby, they discovered he weighed 8lbs 1oz and was not alone - he had an undeveloped twin attached to him.

Dr Anurag Singh, Professor of Paediatrics at the hospital said the newborns were a rare case of parasitic twins but could hopefully be detached in a surgery soon.

'It is definitely a rare case of parasitic twin where the second baby is not fully formed,' he said. 

'They luckily have separate hearts but share the internal mammary artery. This could make it little complicated to operate but chances of saving the baby is high as it is healthy.'

'We are monitoring the condition of the strong baby and taking help of cardiologist to plan a surgery as soon as their condition is stable.'

Parasitic twins are usually a result of a delay in the separation of embryos during conception. 

They are formed when one embryo maintains a dominant development at the expense of the other.

Unlike conjoined twins, one is incompletely formed or wholly dependent on some bodily functions of the complete fetus. 

Cases of parasitic twins are rare and believed to account for just one per one million live births.