United Kingdom, April 3 -- 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 ...