According to a source, Kutcher knew that Moore would write about their 2003 miscarriage in her memoir "Inside Out", reports usmagazine.com.
"Ashton knew what was coming. He had a heads up on what is in the book," the source said, adding: "He's not mad or disappointed. This is Demi's truth, and he always felt sympathetic toward her. He knows her story and that her upbringing was difficult."
In the book, which will release internationally on September 24, Moore has opened up about how she became pregnant soon after she started dating Kutcher in 2003.
Six months into the pregnancy, the actress lost the baby, which she planned to name Chaplin Ray. Moore and Kutcher tried to get pregnant through fertility treatments after they got married in 2005. But the couple was unsuccessful. They split in 2011 and finalised their divorce in 2013.
According to the source, the break-up was difficult for Kutcher.
"It was a hard process when their marriage ended, and he was very much aware of it. But they both needed to move on and find their way separately," the source said.
He doesn't regret his relationship with her.
"It's a chapter of his life that he has moved on from. He's in a very different place now. But he knows without that experience and relationship he wouldn't be where he is or who he is. He had to go through it to get to this place and he's grateful for it," added the source.
( With inputs from IANS )