Almost 18 years ago to the day, tiny twin babies were born three months early at Bradford Royal Infirmary.

Kimberly Jade Howell and her brother Leo each weighed less than a bag of sugar. Their mum Teresa was stunned when she saw them. “Leo was 1lb 13.5oz and Kimberly was only 1lb 10oz,” she says. “They were so small and fragile-looking, like skinned rabbits. I was scared to touch them.”

Of the two, Leo was the stronger and soon began to thrive, but Kimberly was very weak and it was feared she may not survive.

Thankfully, she did and, 18 years later, the twins have reached a milestone in their lives, celebrating their 18th birthdays.

“It is fantastic to see them today, because when I first saw them I didn’t think they would pull through,” says Teresa, of Wyke. “When I saw them I got a nose bleed from the stress of it all. I couldn’t get any nappies to fit them, not even the really small ones. They just lay on top of the nappies, connected to all the wires and tubes.”

The siblings find it hard to believe they were so small. “My auntie was showing me pictures the other day,” says Kimberly. “I think ‘wow, how tiny’. I always wonder how my mum coped with everything.” Adds Leo: “I like looking at pictures of us when we were born.”

Teresa, of Wyke, had a trouble-free pregnancy, although conceiving came as a shock as she was taking contraceptive pills. With two children – Leanne, now 28, and Daniel, 22 – she had not planned to have any more.

“It was more of a surprise at the scan, to find out I was expecting twins,” she recalls. On the night she gave birth she had popped out to play bingo. “I won a fiver and ended up in labour,” she laughs.

She had a Caesarean section and was not awake for the birth. When she came round she was eager to see her babies and asked her husband Michael how they were.

“I knew he had seen them, but when he came back to me he was so quiet,” she said at the time. When she saw them for herself she understood why.

“They were lying side-by-side, connected to loads of tubes and they were being ventilated. They were so tiny – we could see their little bones through their skin.“ While most mothers return home with their babies within hours or days, it was three months before Teresa was able to take Leo home, and four months before she took Kimberly to join him. At seven weeks, Kimberly was transferred to Leeds General Infirmary after suffering lung problems.

Teresa became so anxious she began to keep a diary detailing their progress. “I found it helped me to relax,” she says. “And I wanted to be able to look back with the twins when they were older and remember what it was like at the time.”

One entry reads: ‘Kimberly still very poorly. Doctors gave her X-ray. It didn’t look good. They decided to put a camera down her throat to see what was causing the problem.’ They discovered that her lungs were crushing her heart, requiring a lengthy operation. “They took half her lung away,” says Teresa, who works at her local Co-op.

Kimberly remained on the danger list for some time. At one point doctors shaved her head to insert a drip as the tiny veins in her arms and legs had collapsed.

Teresa, now 47 and a grandmother, was elated when she was able to bring them home. “It was brilliant seeing them in their Moses basket,” she said at the time. “Leo did not sleep through the night until his sister came home.”

In infancy Kimberly was in and out of hospital. She still suffers from asthma – which affected her a lot as a child – but is otherwise a healthy teenager who loves socialising with her friends and listening to music. “I like Ed Sheeran, Katy Perry and Bruno Mars.”

Her experience has lead to her wanting to become a midwife. Currently studying at Bradford Academy, she is hoping to find a work placement to learn more about the profession.

Leo is mildly autistic and suffers from dyslexia and ADHD. He had a hard time at school and is aware of his limitations.

“It was horrible, I spent years getting bullied,” he says. He has now changed schools and attends the same school as his sister, where he is happy. He enjoys bike riding, drawing and “chilling with friends.”

He adds: “I like washing cars and would like to find a job as a car salesman or valeter, but because I have difficulties, it is very hard for me.”

The twins celebrated their birthday earlier this month with a party with family and friends. Michael, the manager of a chemical company, sang at the celebration, where his friend Mark provided his DJ services.

“It is amazing to see Kimberly and Leo today after what we all went through,” says Teresa. “I used to pray every night for them to be okay. When I look at them it is hard to believe they were once so small they could fit in my hands.”