Remarkably, Debbie was still taking the contraceptive pill when she fell pregnant with baby son Kyle - and she needed her reading glasses to look at the pregnancy test results!
Debbie, a jewellery assistant, who lives with her partner Paul Clarke, 45, a heavy goods vehicle driver, wasn't planning any additions to her family.
She already has two sons, Mark, 26, and Brandon, 11, and a daughter Hayley who tragically died just a week before her 18th birthday. She is also a proud grandmother to Mark's daughters.
She thought her days as a mother nursing a newborn baby were definitely over, and had been using the contraceptive pill to make doubly sure.
"I'd already given birth to three children, and thought that those days were definitely over," says Debbie.
I was on the contraceptive pill just to make sure, but I never imagined I could ever have fallen pregnant at my age. I'm a grandmother and I love looking after my granddaughters - I never thought that I would be looking after another baby of my own.
Debbie only discovered she was expecting a baby last March, when she was already five months pregnant.
"I'm a slim build anyway and Mark noticed that my stomach was slightly protruding and he started teasing me that I was starting to put on a bit of weight.
"He joked that I could be pregnant, which seemed impossible, as I was still having my periods. But it niggled in the back of my mind about why I had put on a bit of weight. So I did a pregnancy test just to make sure.
"I thought I was throwing my money away doing a test as I couldn't possibly be pregnant, but when it showed positive I couldn't believe it.
I had to put my reading glasses on to read the pregnancy result, and I was so incredibly shocked. I went out and bought another three tests to make sure. And each one showed the same positive result.
Debbie then went to see her GP, who thought that she was joking when she told him she was pregnant.
"He was so shocked when he realised I was telling the truth. He nearly fell off his chair," explains Debbie.
"He had never before seen a woman of my age fall pregnant naturally. He wished me good luck and booked me in to see the midwife. When I broke the news to my sons afterwards, they were shocked. They never expected another addition to the family."
Debbie was worried about her age, but she had a textbook pregnancy, with only a small amount of morning sickness in the first few months:
I had been so worried because of my age about whether I was even going to be able to carry the pregnancy to full term because I knew there was a high chance of me losing the baby or giving birth prematurely.
"But I felt incredibly healthy all the way through and only had a tiny bit of sickness."
Debbie had been offered a scan to check for deformities or abnormalities, but she refused.
"I knew there was a higher chance of my baby having a deformity, but I was determined to keep the baby whatever happened, and I knew I would love it whatever the outcome," she explains. "So I didn't want to know, and instead wanted to let nature run its course."
Debbie went into labour in June, and after a normal labour, gave birth naturally to son Kyle at Northampton General Hospital, weighing a healthy 7lb 11oz.
"It was amazing to hold him in my arms afterwards, and I felt the same rush of love that I had felt with my other children," says the proud new mum.
I do get more tired than I did before, especially getting up to do the night feeds. But I do love being a mum again. I am worried about being an older mum and not seeing Kyle grow up, but he has his dad too, who is younger than me.
"Being an older mum has its advantages as I've done it all before. I'm not anxious about every sniffle. And I'm hoping that having a baby at age 53 will help keep me young."
Dawn Brooke, from Guernsey became the world's oldest mum through natural conception at the age of 59, in 1997.
Mark Sedler, Consultant Gynaecologist at CARE Fertility, said: "Falling pregnant at this age without any form of fertility treatment and for the baby to be born healthy and well is remarkable. The odds are about the same as winning the lottery. It is extremely rare.
"After the age of 46 it is unlikely that women produce good enough quality eggs to fall pregnant, and so in fertility treatment, donor eggs are used.
"Even if they fall pregnant it is then more difficult for a woman of this age to carry a baby to full term. It is more likely that the pregnancy miscarries. For a woman of this age to fall pregnant naturally and for the mother and baby to be both healthy and well is most remarkable."
What an incredible story.
Night feeds and nappy changes at 53, could you do it?
More on Parentdish: Meet the mum who can't stop getting pregnant despite being on the pill!