A photo grab from Azarenka's Twitter account shows the announcement.
World number six Victoria Azarenka said on Friday she will miss the rest of the season because she was having a baby.
The 26-year-old Belarussian, who won the Australian Open in 2012 and 2013, did not play at Wimbledon this year due to a knee injury. The former world number one will return to the circuit.
"While recovering from the knee injury that I sustained at Roland Garros, I received news from my doctor that my boyfriend and I are going to be become parents at the end of this year," Azarenka said on her official Twitter account.
"While I will miss competing in the sport that I love this season, I am excited for all that's ahead.
The two-time Grand Slam champion hints she plans to resume her career after the baby is born.
"I have been truly inspired by so many strong female athletes who return to the very top of their sport after having children, and I plan to do exactly that."
Kim Clijsters did exactly that in recent years, coming out of retirement in 2009 after the birth of her daughter and going on to win three more major titles.
She made the announcement Friday just as the International Tennis Federation was about to release its list of players for next month's Olympics. Azarenka's name was on the roster even though she won't be competing in Rio.
