Conjoined California twins separated in a 17-hour operation have been reunited for the first time since the surgery.

Eva and Erika Sandoval have been recovering in separate beds in the same room, but they could not see each other well.

So the two-year-olds' parents and intensive care team at Lucile Packard Children's Hospital Stanford carefully carried Erika and placed her in Eva's bed to say hello.

It is the closest the twins have been since they were separated on December 6.

"It was such a thrill for us to see the girls next to one another again," said the twins' mother Aida Sandoval.

Dr Meghna Patel, who is caring for Erika in the paediatric intensive care unit, said both were doing well. "They have had no significant complications," she said.

Before surgery, the girls shared a bladder, liver, parts of their digestive system and a third leg. Each girl retains portions of the organs they shared, and each still has one leg.

The third limb was used for skin grafts to cover surgical wounds. Both girls will probably need a prosthetic leg, doctors say.

The twins, from the Sacramento area, are awake and breathing without ventilators and are expected to continue recovering from surgery in the Palo Alto hospital for another week before moving out of intensive care to an acute care unit.

As few as one of every 200,000 births results in conjoined twins. About 50% of such twins are stillborn, and 35% survive only one day, according to the University of Maryland Medical Centre.

Only a few hundred operations have been performed successfully to separate conjoined twins. Stanford doctors had calculated a 30% chance that one or both twins would not make it through the operation.