Dakota and Scarlett McKewan with their mom. Picture: YouTube screenschot

London - Looking confidently out on the world, blue-eyed twins Dakota and Scarlett McKewan could hardly seem more content.

At nine months old, their happy faces show no sign of their dramatic fight for survival in the womb as they were operated on by laser to save them from a deadly condition.

Bianca McKewan, 35, was 13 weeks pregnant when she was told she and husband Trevor, 45, were expecting identical twins.

But just three weeks later doctors had to tell them the babies had the rare twin to twin transfusion syndrome.

It meant one twin was receiving a larger share of the blood supply and nutrients, putting a strain on her heart. Meanwhile, the other twin was being starved of nutrients. Without intervention, both would die.

McKewan, a nurse, said: "It was devastating when we knew how their lives were at risk. They were literally killing each other in the womb before they were even born."

The couple, from Croydon, south London, were told that the condition had already progressed to such a serious stage that a rare and risky procedure was the twins’ only hope.

An incision would be made in the mother’s stomach, which would allow a laser to divide the blood vessels in the placenta which joined them. If the surgery was successful, it would raise the survival rate for at least one twin to 75 to 80 percent.

McKewan said: "We were worried about the operation as we knew that in itself it could be fatal for the babies – but we knew we had no option if we wanted to try to save their lives."

The operation at King’s College Hospital in London went well. But the couple had to wait another two weeks to find out whether the new blood supply was working effectively. There were also fears that Mrs McKewan could miscarry as a result of the procedure.

"It was incredibly scary. Each day I would just hope and pray that they would hold on," she said. Fortunately, Scarlett and Dakota did, and were eventually delivered by doctors at 27 weeks.

The proud mother said: "They have such a close bond. They’d had a battle for survival which began in the womb and they have fought all the way through."