She told People magazine: "We thank God for our blessing", and posed for a picture with her growing baby bump.
Speculation about her pregnancy surfaced in April when she postponed her 'Unbreakable' tour, saying she wanted to focus on planning a family with her husband, Wissam al-Mana.
She was recently spotted in London shopping for baby essentials.
The People magazine quoted a source close to the Jackson family as saying: "She is super excited about her pregnancy and is doing extremely well. She actually feels very good about everything."
In a video posted on Twitter in April, she told her fans that she was postponing her world tour because "there's been a sudden change".
"I thought it was important that you be the first to know. My husband and I are planning our family," she said, adding: "Please if you can try and understand that its important that I do this now."
She went on to say: "I have to rest up, doctor's orders."
Profile: Janet Jackson
- Janet Damita Jo Jackson was born on 16 May 1966 in Gary, Indiana in the US
- She is the youngest of nine children and sister of late pop icon Michael Jackson
- She released her first album Janet Jackson in 1982
- She has a total of 11 albums with the most recent, Unbreakable, released in 2015
- She is a seven-time Grammy award winner
- She began her career with the family's reality TV series The Jacksons in 1976 and has since appeared in several movies such as Tyler Perry's Why Did I Get Married
- The singer married her third husband, Qatari billionaire Wissam al-Mana, in 2012.
Janet Jackson is far from the only famous face to give birth later in life.
Oscar-winning Halle Berry had her second child at 47, three years ago, and John Travolta's wife Kelly Preston gave birth to her third child at 48.
Geena Davis - best known for her role in Thelma and Louise - became a mother later in life after falling in love with an Iranian-American neurosurgeon in her 40s. Her first child, a girl, arrived when she was 46, followed two years later by twin boys.
Then there was Swiss billionaire Maria Louis-Dreyfus, who gave birth to twin girls in March 2016, aged 53.
But these mothers - and Jackson - are all positively young when compared to the world's oldest new mothers.
In fact, there are at least three women in India who claimed to have carried their children to term when at least two decades older than the pop singer.
Daljinder Kaur, who may be as old as 72, although she claimed to be just 70, gave birth to a son in April 2016 after three attempts at IVF.
Each time, the births caused a debate over the ethical issues surrounding having a baby so late in life - especially after Maria del Carmen Bousada de Lara, the Spanish woman who once held the title of the world's oldest mother, died three years after having twin boys.
All three are understood to have used donated eggs in order to have their children.