At the time he shrugged off suggestions that fatherhood would dampen his love of motorcycling.
"They say you slow down when you get married, but in my first year of marriage I won the title," said Stoner on the eve of the season.
"When I found out we were having a baby, I won it a second time. I don't think that's the case (that you slow down)."
Despite his blistering start to the season, Stoner has been critical of a series of technical changes to the sport that he claimed were undermining the championship.
This year's MotoGP bikes are 1000cc as opposed to the 800cc of old, while manufacturers such as Kawasaki and Suzuki no longer field factory teams, leaving just Honda, Ducati and Yamaha with official squads.
He has also been battling cramps in his arms that prove particularly painful under braking. Those problems came to the fore in the season-opener in Qatar, where he finished third before going on to secure wins in Spain and Portugal.
Stoner joined the elite MotoGP class in 2006 with a satellite Honda team after working his way through the 125cc and 250cc ranks following his debut as a 125cc wildcard at Donington, England, in 2001.
His switch to Ducati in 2007 proved an inspired decision as he won the MotoGP season-opener in Qatar, followed by nine more victories that propelled him to the world title.
He moved to the factory Honda team last year and clinched his second title on home ground at Phillip Island, having already won nine races. Stoner closed the season with a 10th victory in Valencia.
Nine-time world champion Valentino Rossi, one of Stoner's great rivals, said he was shocked by the Australian's decision.
"It's a huge surprise to me as it is for everyone else," said the Italian. "It's bad news for the world of MotoGP.
"At the end of the season, we are going to lose a great rider and a great rival, but it's his decision."
- AFP
