Abby and Erin were delivered by C-section 10 weeks prematurely Picture: AP
For the first time, conjoined twins Abby and Erin Delaney can sleep in separate beds.

The 10-month-old girls from North Carolina were born connected at the head, an extremely rare condition. Following months of planning and preparation, the pair underwent a successful 11-hour separation surgery last week at Children's Hospital of Philadelphia in southeastern Pennsylvania, according to the hospital.

“Separating conjoined twins is a very complex surgery followed by a long and complicated recovery, but we are very hopeful for a positive outcome,” Jesse Taylor, a plastic surgeon who co-led the operation with neurosurgeon Gregory Heuer, said. “Erin and Abby are now recovering in our Paediatric Intensive Care Unit under close monitoring by our expert teams.”

With identical twins, an embryo splits in two early in a pregnancy; but with conjoined twins, the embryo does not separate all the way and the twins remain connected, according to the University of Maryland Medical Centre.

Abby and Erin’s parents, Riley and Heather Delaney, learnt their girls were conjoined early last year when Heather was about 11 weeks pregnant.

Although it was too soon to know whether the twins would be able to be separated, Heather started travelling from North Carolina to Pennsylvania for her prenatal care. Eventually, she moved into a hospital facility in Philadelphia for mothers carrying babies with complex congenital conditions, according to the hospital.

On July 24, 2016, Abby and Erin were delivered by C-section 10 weeks prematurely, the hospital said.

Children's Hospital of Philadelphia said about 30 doctors, nurses and other medical personnel worked to separate the twins.

The hospital said the twins will likely have additional surgeries but plans to send them home later this year.

“When we go home, it's going to be a big party,” Heather said. “Welcome home, baby shower, first birthday.” - Washington Post