Deontay Wilder has claimed that his ex-girlfriend Helen Duncan "injected" his sperm into her after intercourse to conceive his eldest child.

The 40-year-old boxer is father to eight children and revealed all in a graphic story about how his eldest daughter Naieya was conceived.

Wilder told Piers Morgan Uncensored: "She injected my sperm in her and ran into the bathroom and locked the door, and that's how we had her - truth be told. She don't even know that I know this."

When an astonished Morgan quizzed Wilder on how he knew about his ex-girlfriend's fertility plan, the former heavyweight world champion replied: "I'm smart."

The boxer went on: "You know, when we was having sex, when I came, I used to c** on her stomach. I used to fold my towel nicely by the bed because I would want to wipe it off her stomach. This particular time, she chose that she wanted to have a baby by me because I was the best thing that ever came into her life.

"So during that time, I did what I had to do. I had a good nut, and I nutted on her stomach. This time, I went and got the towel and tried to wipe it off, and she hit my hand so hard."

Wilder explained that his suspicions were confirmed when he read his ex's journal unbeknownst to her.

Deontay and Helen's daughter was born in 2005 with spina bifida - a defect where the spine does not close completely - and he revealed that his former girlfriend wanted to terminate the pregnancy when she learned of this, although he "felt like she deserved to live".

He said: "I wanted to take up on this opportunity of taking care of a girl that was born with spina bifida - a child that was in need."

Wilder has previously been open about raising Naieya, as doctors initially believed that she would never be able to walk because of the condition.

The American fighter told ESPN in 2017: "My daughter is doing wonderful now. You could never tell that she has spina bifida. She still walks with a limp because she had (five) surgeries when she was a baby.

"She still has to be catheterised, but she still manages to maintain her own. She is a very strong young lady. She will be a very strong woman. She has no choice, with who her daddy is."