WATCH: Mother's delight as conjoined twins prepare for their first day at school

Rosie and Ruby Formosa, who were born joined at the abdomen and shared part of the intestine, needed an emergency operation to separate them when they were born in 2012.

Their parents, Angela and Daniel Formosa, were told the girls had a low chance of survival when medics discovered they were conjoined.

But after a successful separation operation at London’s Great Ormond Street Hospital (Gosh), the identical twins lead happy and healthy lives and are preparing to start school in September.

The four-year-olds, from Bexleyheath in Kent, are “very excited” to be starting school like their big sister Lily, nine, Mrs Formosa said.

“Four years ago it wasn’t in my mind that this would ever happen,” she said.

“When I was pregnant I didn’t think I’d ever see their first day at school so it is really amazing and all thanks to Gosh really.”

Mrs Formosa said it was “heartbreaking” when she discovered the girls had the rare medical condition – it accounts for one in every 200,000 live births.

“At 16 weeks they sent me to King’s College Hospital and it was there that they discovered the connection between the girls,” she said.

The girls were born at University College Hospital in London by caesarean section when Mrs Formosa was 34 weeks pregnant.

Within a couple of hours of being born, they were taken to Gosh for emergency surgery because of an intestinal blockage.

The operation to separate them took five hours and the girls were well enough to go home when they were just three weeks old.

Great Ormond Street Hospital is the leading centre in Europe for the care of conjoined twins, performing the first successful separation surgery on conjoined twins in 1985. It has since cared for 27 sets of conjoined twins.