Former world No 1 Naomi Osaka announced on Wednesday that she is pregnant and will be taking a break from tennis until 2024.

"I know that I have so much to look forward to in the future, one thing I'm looking forward to is for my kid to watch my matches and tell someone, 'That's my mom' haha," she wrote on Twitter, accompanied by an ultrasound picture of a pregnancy scan.

"2023 will be a year full of lessons for me, and I hope I'll see you guys at the start of the next one cause I will be back at the Australian Open 2024. Love you all infinitely," she added.

The 25-year-old Osaka has not played a tennis match since September and her withdrawal from the Australian Open, which starts next week, had puzzled many observers.

Her social media posts in recent months had shown her traveling in Europe with her boyfriend, American rapper Cordae.

The two have been together since 2019.

Osaka had not explained her absence until Wednesday, when she posted what she called "a little life update for 2023".

Osaka's last tournament appearance was at the Pan Pacific Open in Tokyo in September, where the home favorite withdrew before her second-round match, complaining of abdominal pain.

The top ranked player in the world in 2019, the Japanese star — who grew up in the United States — is now ranked 47th in the world.

Osaka has won four Grand Slam singles titles with triumphs in the Australian Open in 2019 and 2021 and the US Open in 2018 and 2020.

She had been open about her struggles with mental health and depression in the past and took a break from the sport after the French Open in 2021 before returning to compete at the Tokyo Olympics later that year.

With a string of lucrative endorsement deals across the globe, including with several top Japanese brands, she was named the world's top-earning female athlete for 2022 by Forbes, with reported earnings of $51.1 million.

Her commercial success was not reflected on the court last year however as she suffered first-round defeats at both the French and US Opens and withdrew from Wimbledon with an Achilles injury.

Osaka has also been vocal in support of various causes and in 2020 she said she wouldn't play in her semifinal at the Cincinnati Open in response to the shooting of black man Jacob Blake in Wisconsin. Following her statement the tournament paused for a day.

Osaka's recent absence from the tour had promoted speculation over her future in the game, but on Wednesday she said her break has given her a new perspective on the sport.

"These few months away from the sport have really given me a new love and appreciation for the game I've dedicated my life to," she wrote.

"I realize that life is so short, and I don't take any moments for granted; every day is a new blessing and adventure."

AFP