Michael Lockwood and Lisa Marie Presley
08/05/2008 at 03:00 PM EDT
Lisa Marie Presley is pregnant with twins, her rep confirms to PEOPLE.
"She wanted it really to be kept a secret for a long time," the singer's mother, Priscilla Presley, tells Entertainment Tonight
, which broke the news. "And I think women should, because they should be able to announce what they're having and when it's time to make the announcement."
Presley, 40, who is expected to give birth in the fall, has two teenage children, daughter Riley, 19, and son Benjamin, 15, with ex Danny Keough.
The twins will be Presley's first children with husband Michael Lockwood.
Speculation about Presley's pregnancy first surfaced after the Daily Mail
published unflattering photographs and alleged that the singer had an unhealthy appetite. Presley sued for libel, and the paper later apologized. She also blogged
about the experience, writing, "I accept their attempt at redemption."
At the time, Presley told PEOPLE,
"Yes, I am swollen. And I am going to gain weight in a city where if you're not a minus size 0, you are fat."