“The twins, who were joined at the upper part of their abdomen, were successfully separated, giving them a new lease of life," the Narayana Health City said in a statement.

 Conjoined twins are extremely rare with an estimated incidence of 1 in 50000–100000 births.Conjoined twins are genetically identical, and are, therefore, always the same sex. They develop from the same fertilized egg, and they share the same amniotic cavity and placenta.

 Twinning occurs one of two ways:

1. A woman releases two eggs instead of the usual one or
2. Produces only one egg that divides after fertilization.

 If woman releases two eggs, which are fertilized by separate sperm, she has fraternal twins. When a single, fertilized egg divides and separates, she has paternal or identical twins.

In the case of conjoined twins, a woman only produces a single egg, which does not fully separate after fertilization during the first few weeks after conception. The partially separated embryo develops into a conjoined fetus.An embryo develops from a zygote.Zygote is the single cell resulting from the fertilization of the egg by the sperm.

Conjoined twins may be joined at any of these sites:

• Chest (Thoracopagus): twins are joined face to face at the chest.It is commonest type and account for 42% cases.
• Abdomen ( Omphalopagus):twins are joined near the belly button.
• Base of spine (Pygopagus) twins are commonly joined back to back at the base of the spine and the buttocks.
• Length of spine (Rachipagus) : twins are joined back to back along the length of the spine.
• Pelvis (Ischiopagus) twins are joined at the pelvis, either face to face or end to end.
• Trunk  (Parapagus) twins are joined side to side at the pelvis and part or all of the abdomen and chest, but with separate heads.
• Head (Craniopagus) twins are joined at the back, top or side of the head, but not the face.

The surgery for separation of conjoined twins is a delicate and risky procedure.It requires extreme precision and care.

Image source: stayathomemum