Martin Crowe, former New Zealand cricket star, died at the age of 53 in March 2016 from lymphoma.
Downes revealed that she and Crowe tried for a child into their mid-40s, and that she had fallen pregnant to Crowe before a miscarriage.
In the TVNZ Sunday interview, Downes said it would have been "amazing" to have a child with Crowe.
"When you meet your soulmate, you just know how special that is. And wouldn't it be amazing if we could have a child that was born out of our love?," she said.
"I am the eternal optimist. My mother was born when her mother was 47 so I thought 'Well I can do it'. So we did try.
"You think, 'Oh I might be pregnant this month'. And when you're not, that in itself is like losing a baby every month. That's what it felt like to me."
"Marty wants me to be joyful again. He wants me to shine again. He wants me to thrive. And that's what I'm doing," Downes told Sunday.
Downes is to release a memoir of her experience, Life, Loss, Love, this week.