US Weekly is reporting that the firstborn for the couple arrived on Friday, September 12.

The magazine also 'confirmed' 40-year-old Mendes' pregnancy in July. This was despite Mendes laughing off rumours that she was even pregnant.

She went on The Ellen DeGeneres Show in February, when the rumours first arose.

"It's so ridiculous," she said. "It all started because I didn't want to go through the scanners at the airport. You know those X-ray scanners, which are really creepy? They basically see you naked, right? And not only that, but there's a radiation aspect to it, so I always opt out."

Mendes met Gosling, 33, on the set of The Place Beyond the Pines in 2011.

They began dating that same year, when Gosling opened up about his desire to be a father.

"I'd like to be making babies but I'm not, so I'm making movies," he told The Times.

"When someone comes along, I don't think I'll be able to do both and I'm fine with that. I'll make movies until I make babies."

Fairfax Media