During the most recent episode of her podcast show Labyrinths, Ms Knox took a pregnancy test before revealing that it had come back positive. Upon seeing the result she shouted: “Thank goodness, we did it.”
Ms Knox became infamous when she was convicted of the 2007 murder of her former roommate Meredith Kercher in Perugia, Italy.
At the time prosecutors branded the 21-year-old’s slaying as a “sex game gone wrong”.
But in 2015 the Italian supreme court acquitted her and former lover Raffaele Sollecito.
Speaking on the podcast, Ms Knox said: “That’s right, we’re pregnant, and we’ve been recording audio of our own experience since day one.
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Ms Knox, who married Mr Robinson in 2018, added: “We thought it was a straight line from unprotected sex to baby.
“It was abdominal pain like I have not experienced before. I was shaking.”
She added: “I thought I knew exactly what I wanted to do with my first pregnancy and to have it not come to fruition, not through choice, felt like a betrayal.
“Do I have bad eggs? Am I too old? Did something happen to me while I was in Italy?
“You remain haunted by the life that never was.
“As soon as I learned it wasn’t alive, I tried to divorce those two ideas in my head, that was not my baby, it doesn’t have a name.
“It was just your baby for that amount of time, we already had a baby it was just only six weeks old, who is that baby?
“I don’t know that baby, I don’t think I ever will.”
She also described painting a mural in the baby’s room and cried as she recalled telling the story to her mother.
She added: “I could tell she wanted to hug me but I just couldn’t.
“It’s Covid and we’re not supposed to hug each other.”
Ms Kercher had studied in Italy for just two months before she was murdered in the apartment she shared with Ms Knox.
Both her and former boyfriend Mr Sollecito, 36, were jailed for her murder a year later.
They were released from prison in 2011 following a successful appeal against their convictions before they were both found not guilty in 2015.
Rudy Guede is the only person handed a conviction in connection to the case.
He was released from prison at the end of last year.
Since overturning her conviction, Ms Knox has returned to the US where she has built a large media profile.