He weighs as much as a six-month-old baby but newborn Maoama Ala has stunned Melbourne doctors - and his mother - after being born almost double the average size of a newborn.

Maoama tipped the scales at 6.3kg when he was born on Tuesday at Melbourne's Sunshine Hospital.

He was delivered by caesarean one week early on the advice of doctors, who were concerned about his large size.

They expected the baby to weigh around 4kg, but when he arrived he weighed 2kg more.

“We were all a little bit shocked and surprised by it,” Obstetrician Lauren De Luca told reporters.

“This is off the charts.”

Ms De Luca said baby Maoama weighed as much as a three to six month old baby.

At 6.3kg Maoamo weighs almost double Eli Richards, who was born weighing 3.6kg.

AAP

Baby Maoama, who is too big for the newborn size nappies his parents brought to hospital, is already wearing three to six month old size clothes.

He is a fourth child for dad Maoama, whom he is named after, and mum Teuaililo Ala.

The couple, originally from Samoa, already have nine-year-old twins and a six-year-old.

Baby Maoamo with his father and mother, Maoama and Teuaililo Ala.

SBS

Ms Ala said she was surprised to meet her “huge” baby.

“He was too heavy on my chest,” she said, laughing, of the moment he was handed to her.

Maternity Ward Manager Lisa Smith said it was an unusual event.

"It's something that will often only happen in the careers of midwifes and obstetricians maybe once,” she said.