The bouncing baby has stolen the heavyweight crown from Suzie Devendale, who was thought to be Britain's heaviest baby girl after weighing a mega 12lbs 12oz when she was born four weeks ago.
Niamh's dad Sean O'Halloran, 34, told The Sun that he and partner Elaine Martin, 32, were expecting a big baby, but one closer to the 10 to 11lbs mark! He said: "When she got weighed, I thought 'bloody hell'. Everyone was shocked. She was off the charts."
Elaine - who gave birth at Ipswich hospital said she hadn't noticed the enormous proportions of her baby bump until colleagues commented on her size! Niamh is the couple's first baby, and was born by Caesarean section on November 8 2011.
Now four months old, Niamh has put on just a few more pounds from her birth-weight, after initially losing some weight in the weeks after her arrival (as all babies do), but she is still above average for her age.
Miss Martin, who is an acute medicine nurse at Ipswich hospital, and Mr O'Halloran, who is a research scientist, are planning to marry later this year.
Wow! What a whopper! Did any of yours come close to Niamh or Suzie's weights?