With cheeky smiles and waving fists, twins Maisie and Charlotte Wallis are like any other healthy, happy babies.

But their milestone first birthday on Thursday carried more significance than most.

Maisie and Charlotte suffered in the womb from a condition called Twin to Twin Transfusion Syndrome (TTTS), which meant one got more blood than it could cope with, while the other did not have enough to grow properly.

Mum Michelle Wallis, 28, faced an uphill battle to keep her girls alive, suffering painful procedures which involved using a large needle to drain fluid from her bump.

Then at 29 weeks doctors were forced to perform an emergency Caesarean section when the twins became too distressed in the womb to cope.

"We had a difficult pregnancy, making regular trips to hospital in Nottingham," said Michelle, who lives with husband Stephen, 28, daughter Ashleigh, 10, and son Eric, three, in Apley, near Wragby.

"We found out at 12 weeks I was having twins, which was a shock, then at 16 weeks the TTTS was discovered.

"It's is a fairly rare condition and the problem is not many people know what it is.

"I want to make people aware of it and what it means."

After they were born at a specialist unit in Sheffield, both babies had to be put in incubators. Maisie was 2lb 12oz and Charlotte 2lb 4oz.

A week later they were transferred to Lincoln County Hospital but Maisie took a turn for the worse and had to be cared for in Nottingham, while Charlotte got an infection in her lungs. A fortnight later the twins were reunited in Lincoln, spending six weeks in incubators and two weeks in open cots on the neonatal ward before being allowed home.

"My girls are miracle babies," said Mrs Wallis. "They have come so far although they are both still really small.

"Their development is on track for a nine-month-old, but that's OK as it's what age they should actually be now.

"They just did three months of growing in the world instead of the womb in the world."