Fearne Cotton is quitting Radio 1 after telling her fans she is pregnant with her second child.
The DJ, who is married to Ronnie Wood's son Jesse, said leaving the station was the start of a "new chapter".
Writing on her website, she said she had had "the most incredible decade" working on the station.
Cotton's role presenting the station's Live Lounge will be taken over by Clara Amfo.
Presenter Fearne Cotton has apologised to listeners after a microphone was left on during her Radio 1 show and picked up swearing. The mid-morning DJ was hosting a Christmas party edition of her Live Lounge with guests who included Ricky Gervais and Jamie Oliver.
But the production team accidentally failed to fade out the mic while playing Wizzard's I Wish It Could Be Christmas Every Day, allowing banter to be heard over the music.
She said: "We might have heard some bad language on the radio because one of the mics was still faded up, in the kitchen."
She came on air to apologise shortly after the track had aired, to say sorry to listeners and viewers watching the programme online and on the BBC's red button service.
Fearne Cotton has announced on Twitter that she has given birth to her first child, a son.
The Radio 1 DJ and her partner Jesse Wood, the son of Rolling Stone Ronnie, said on the social networking site:
TV presenter and DJ Fearne Cotton has said she is "over the moon" after announcing she is pregnant.
Cotton has been dating Jesse Wood - the son of the Rolling Stones guitarist Ronnie Wood - since last year.
Writing on her blog, she said: "We are over the moon, morning sickness aside (me, not Jess) and looking forward to the little Cotton Woods arrival."