Their parents Andy and Anna Collier have hailed the survival of the three kids as a miracle.
"When they were born they were just so tiny. They could have each fitted into the palm of our hands," the Daily Mail quoted Anna, as saying.
"When they stopped breathing and had to be resuscitated each time, we thought we could lose them," she added.
Collier gave birth to the triplets at Chelsea and Westminster Hospital on January 6 last year, at 29 weeks.
Isabel weighed 2lb 9oz, Ben 2lb 7oz and Emily 2lb 1oz. They were kept on ventilators in intensive care because they could not breathe on their own.
"I wondered how could anything so small possibly survive," Anna said.
The triplets caught numerous infections but managed to hang on.
But she said that at eight weeks, Isabel stopped breathing.
"It was terrifying. She went blue and limp and lifeless. The doctors managed to resuscitate her. She was so lucky, as she was just seconds from death," she said.
She said that three weeks later the same thing happened to Ben.
"One minute he looked fine, the next he went completely still. He was turning blue before my eyes. I screamed for help and the doctors came rushing over. Luckily they were able to resuscitate him too," she said.
Only two hours later, Emily stopped breathing too. She was the weakest triplet, but doctors managed to save her too.
"I was just standing out in the corridor crying. As the doctors pumped the life back into Emily too I just worried about how much more the babies could take. That afternoon, when we nearly lost them both, I called Black Tuesday," Anna said.
She also said that unbelievably, each baby had to be brought back to life two further times.
"Each time they managed to hold on. The doctors couldn't believe what little fighters they were. If it had just been one baby who nearly died three times, that would have been bad enough. To nearly lose all three of them three times each was an emotional rollercoaster. But I knew these babies were fighters and were going to hang on," she said.
The triplets were discharged after 101 days of hospitalisation. They have pulled through and are now up to average weight.
"Isabel is the motherly one while Emily is the tomboy. Ben is the placid one - he has to be with two sisters," Anna said.
In order to thank the hospital, the parents of the triplets have set up a charity to raise 250,000 pounds for life- saving equipment for the neonatal unit.