The "Ghost" star told The New York Times that she wrote in her new book "Inside Out" that she was pregnant with a girl she was going to name Chaplin Ray before she lost the child six months into her pregnancy.
Moore, 56, who started dating Kutcher in 2003 and married him two years later, blamed her herself for the miscarriage and said she began drinking again after previous substance abuse issues.
She details how she tried fertility treatments after they got married in hopes of getting pregnant again, but began drinking heavily and started using Vicodin.
Moore also claims Kutcher, 41, who now has two children with wife Mila Kunis, was unfaithful to her before they separated in 2011 and eventually divorced two years later. Kutcher's spokesperson did not respond to a request for comment.
The actress also revealed that she suffered a seizure in 2012 while smoking synthetic cannabis and inhaling nitrous oxide at a party with Rumer, 31, one of her three daughters with ex-husband Bruce Willis.
"Part of my life was clearly unraveling," she told The New York Times. "I had no career. No relationship."
Her candid memoir, which will be released on Sept. 24, also reflects on her difficult childhood, in which she found out the man who was raising her was not her biological father and later was raped as a teen.
Moore also writes about her recovery in recent years and her relationship with her daughters.
The "A Few Good Men" star has also revisited another part of her past in putting an updated spin on her famous nude "Vanity Fair" cover in 1991 in which she was pregnant.
"My daughters offered me an opportunity to start to change the generational pattern," she told the magazine. "To be able to break the cycles."