Champion cyclist Lance Armstrong has announced that his girlfriend is pregnant with his fifth child.

Lance, who already has three children with his ex-wife, welcomed his first baby – a little boy called Max – with partner Anna Hansen last June.

The 38-year-old athlete revealed the news via Twitter after setting up a page in the unborn baby's honour.

"Getting ?s today about someone I'm following, a certain @cincoarmstrong. What to say," tweeted Lance on his own profile. "Yet another blessing in our lives. I cannot wait!"

And @Cincoarmstrong's first post on the networking site? "I got 2 arms, 2 legs, a nickname and (I'm) 2 inches long. See y'all in October."

The new arrival will be a brother or sister to ten-month-old Max, as well as eight-year-old twins Isabelle and Grace and 11-year-old Luke.