Twins born 15 weeks prematurely are celebrating beating the odds as they turn 21 years old next week.

Doctors were “not hopeful” when Heather Harris gave birth to her twins Sam and Holly on December 1996, when they should have arrived in April the following year.

The pair weighed one and a half pounds each when they were born and spent the first few months of their lives in hospital.

But their 53-year-old mother – who was 32 and living in Rickmansworth when she gave birth – says she feels “very grateful” her children are now living active lives.

Mrs Harris said: “That year I was working for the press office of British Airways and was at my Christmas party when it happened.

“I was dancing on a table at 2am but when I got home that evening I suddenly started bleeding at 3am and couldn’t call my husband – who was at his own Christmas party – as this was before we had mobile phones.

“I’d had my 25 week scan that day and was told everything was fine, but suddenly found myself being rushed to hospital.”

She was told she need to have an emergency caesarean and lost a lot of blood, but praised the doctors and nurses at Watford General Hospital for the way they handled the birth of her twins – who were conceived through IVF.

Mrs Harris explained: “The staff at Watford General Hospital were unbelievable as they saved their lives.

“However, they were whisked off to Queen Charlotte’s and Chelsea Hospital in Chiswick after they were born, which is now a supermarket.

“They had to get two separate ambulances to keep them alive with all the equipment but I was stuck at Watford General due to losing so much blood.”

She added that once the pair left hospital the following April – the month they should have been born – the problems did not end but they have still managed to lead fulfilling lives over the years.

She said: “It was really horrible at the beginning and it was worrying to have a cold winter that year as they had such small lungs.

“But they have certainly proved everyone wrong and beaten the odds as they still did normal things while they were growing up, such as going to mainstream school in Chorleywood.

“Sam has cerebral palsy so could not walk at first and we nearly lost him when he came out of hospital but he is now at university studying journalism and sport and also plays disability football.

“Doctors said Holly would be frail and although she has dyspraxia, she also has a business walking dogs and is out in all weathers.

“I feel so grateful now though. I’ve taken part in 20 marathons raising money for various charities over the years to give something back because we were incredibly lucky.”