"I've had other things that I'm not going to say because God forbid the world will be in an uproar. But I've been through other similar issues," she said of the miscarriage with her and Machine Gun Kelly's baby, before explaining why it affected her so differently.
"That experience was so much harder than I would've anticipated it being, and I've really analyzed 'Why was that? Why was that so difficult for me?'" said Fox. "Because when I was younger, I had an ectopic pregnancy, I've had other things that I'm not going to say because God forbid the world will be in an uproar."
"But I've been through other similar issues, but not with someone who I was so in love with," she added, referring to MGK.
"And so that love element really made this miscarriage really tragic for me and left me with a lot of grief and a lot of suffering," Fox continued. "So I put it into a lot of writing."
Fox said her other half, to whom she's still engaged, also wrote a number of songs about the miscarriage on his most recent album -- something he's seemingly alluded to, but never confirmed.
"He's written about them in his albums as well, he wrote a couple of songs about the miscarriage," she shared. "So it just felt like something that I could address publicly because it's been addressed in one way through him, so I have a space to express as well."
Fox previously discussed the pregnancy loss while promoting her book on Good Morning Americaearlier this month.
"I had never been through anything like that before in my life. I have three kids, so it was very difficult for both of us," recalled Fox, who shares children Noah, 11, Bodhi, 9, and Journey, 7, with ex-husband Brian Austin Green. "And it sent us on a very wild journey together and separately, and together and apart, and together and apart, and together and apart, trying to navigate, 'What does this mean? Why did this happen?'"
Fox wrote about her miscarriage in the final two poems of the book.
"There is an ultrasound by your side of the bed, 10 weeks and 1 day ... do you think that if she could have, she would have left a suicide note?" she wrote in part.
"But now I have to say goodbye. I close my eyes and imagine holding you tight against my chest as they rip you from my insides," Fox added. "I will pay any price, tell me please, what is the ransom for her soul?”