People magazine on Wednesday published a portrait of the star, her face beaming as she stood on a beach, with an unmistakably protruding belly.
"We thank God for our blessing," she told the magazine.
The younger sister of late king of pop Michael Jackson in April stunned fans by halting a global tour and saying that she and her husband, Qatari tycoon Wissam Al Mana, were "planning our family."
Jackson had not said more since then but was recently spotted by paparazzi shopping at a baby store in London -- and looking like she had the tell-tale bump.
Natural pregnancies are highly unusual, but not impossible, for women past their mid-40s, but in vitro fertilization can extend the age at which women can have children.
Jackson has been discreet about her personal life and did not immediately publicize her 2012 marriage to Al Mana, whose company sells luxury fashion brands throughout Gulf Arab kingdoms.
Michael Jackson was also non-traditional in his efforts to have a family. He had two children with Debbie Rowe, who worked at his dermatologist's office and married him, and a third through an undisclosed surrogate.
Janet Jackson won an international fan base in the late 1980s with her albums "Control" and "Janet Jackson's Rhythm Nation 1814," which brought together pop music and funk with the emerging genre of hip-hop.
The albums were notable for their socially conscious lyrics, in which Jackson identified with women's empowerment, and were accompanied by intricately choreographed live shows.
