Mum Natashia Corrigan gives birth to 6kg baby Brian

They say the best things come in small packages.

Well, that's not quite the case when it comes to baby "Little" Brian Junior.

He could well be Victoria's biggest baby, tipping the scales at 6.06kg when he was born on Tuesday.

He's straight into a size 0 and he needs something bigger than newborn nappies.

Natashia Corrigan was shocked by the size of her new son Brian Junior. Photo / Natashia Corrigan Facebook

His mother, Natashia Corrigan, already had three children and thought nothing else could surprise her. But when she first saw Brian Junior, she couldn't help but feel shocked when she found out her baby, who weighed almost 13.5 pounds and is 57cm long, was double the size of the nation's average baby.

"I dreamed of a little fat baby," Ms Corrigan told 7News.

"I've always wanted a little fat baby and now I've got a big baby."

Brian Junior was born at Mercy Hospital for Women in Heidelberg, in Melbourne's northeast, and registered nurse Julie Kane said it was the biggest baby born at the hospital since it moved to Heidelberg.

Ms Corrigan gave birth naturally and all she had was gas.

Her partner Brian Liddle told 7News the birth was "a bit scary" but everybody was fine.

When hearing little Brian Junior could be Victoria's biggest baby, Ms Corrigan said "oh my goodness, that's awesome".

"I'm still in a bit of shock, this is crazy, I didn't think he'd be this big," she said.

The Herald Sun reported Brian Junior was a kilo larger than Ms Corrigan's last child.

He's straight into a size 0 and he needs something bigger than newborn nappies. Photo / Natashia Corrigan Facebook

She said the hospital staff and her partner helped her get through the record-breaking birth.

"They kept me strong and calm when it seemed like chaos was happening around me," she said.

"Because he was so big it was a bit hard to get him out, and they had to get a few extra staff members to come in and help.

"This is the first pregnancy I've got to experience with a natural labour, the longest I've ever been pregnant and I've got the fat little man that I wanted."