When doctors reassured Jennifer Foreman her unborn baby would not weigh more than 8lb she hoped she could trust their judgment.
But after putting on a staggering five stone during the course of her pregnancy, she was right not to be so confident.
Her son Christopher eventually entered the world at a thumping 13lb 2oz – the weight of the average three-month-old – making him one of Britain’s biggest ever newborns.
Miss Foreman heard a cracking sound in her pelvis at the start of her six-hour labour and told doctors she feared the baby was too big, but carried on delivering her son naturally.
Miss Foreman, 26, an office manager, said: ‘The midwife put him on the scales and then took him off again to reset them as she thought they must be wrong. So they weighed him again three times just to make sure. They were all absolutely amazed that I’d given birth to him naturally – and so was I.’
Miss Foreman, who lives with partner Alan Stirzaker, 40, a delivery driver, discovered she was pregnant in February last year.
But her bump grew so rapidly that she was tested to see if she had gestational diabetes.
The test proved negative but at 28 weeks her bump was so big that she had to hire a cleaner and she couldn’t get in and out of the bath by herself.
The couple were worried that their second baby was going to bigger than their three-year-old daughter, Isabelle, who had been born weighing 9lb 14oz.
However, doctors reassured her he would be a normal size.
Miss Foreman went into labour in October at Burnley General Hospital.
At Christopher’s six-month check up he weighed 25lb. The average weight for a baby his age was just over 18lb.
He is now nine months old, weighs 28lb 11oz and wears clothes for an 18-month-old child.
Britain’s biggest baby was Guy Carr from Cumbria, who weighed in at 15lb 8oz in 1992.