Aspin, already mother to Fielder-Civil's son Jack, told Reveal that she found out about her pregnancy four days after his collapse and hospitalisation.
"I don't agree with abortions, but I couldn't help but think that being on my own with two children, while I was grieving, could be too much to deal with," she said.
"But I thought that I had Blake's life inside me - and there was no way I was going to get rid of it... I whispered it in his ear and even though he was really weak, he smiled."
She added of his collapse: "It was touch and go. The doctors told me to phone his family and prepare them for the worst. It was a horrible, horrible time.
"It was really scary. We didn't know if Blake would make it through as he was in a coma and his organs just seemed to be shutting down."
She said of Fielder-Civil's relationship with Amy Winehouse: "Amy used to phone Blake late at night and he'd speak to her for two to three hours at a time.
"Sometimes I would get annoyed. She would say all sorts of things about how much she loved him - she was always telling Blake she loved him.
"If he'd wanted to be back with Amy, he had plenty of opportunities to go back to her. But he chose to be with me."
She added: "In the end I just started feeling sorry for her.
"Blake used to tell Amy, 'For somebody so tiny, you cry too much'. He was her therapist. He'd tell me that they were more like brother and sister than lovers. And that's the way I saw it."
Aspin said that Fielder-Civil is recovering and could be allowed to go home as early as this week.
The full feature appears in Reveal, on sale now. Read the full interview with Sarah Aspin at Reveal.co.uk.