Jo Whiley at the Radio 1 studios announcing her pregnancy - with a T-shirt bearing the slogan 'I slept with Chris Moyles last night'

The 42-year-old presenter, who already has three children - India, Jude and Cassius - with her Virgin Records executive husband Steve Morton, admitted that it was "not expected", but said she was very excited.

Blonde Jo, was wearing an 'I Slept with Chris Moyles' T-shirt during the hand over of her show, and joked with him that she was expecting his child, before later revealing that she is actually pregnant.

She said: "I am having a baby, but it's not technically your baby" she told the gobby presenter, 34.

"I'm announcing it now, but I'm too subtle aren't I?" she added.

"So to all of my mates that I haven't managed to tell yet, I'm really sorry about doing it on national radio!"

"Jesus, so you're pregnant again! It's like a baby factory at your place!" joked shocked Chris.

She added: "I'm a baby machine – there's an army of children in our family! Every day is fat day for me at the moment - I can't stop eating food!

"It was very unexpected but it's very exciting,' she told listeners. We don't know the sex. When we were in the doctor's, they asked if we wanted to find out and we had a big argument about it in the middle of the surgery!

When asked how she was feeling, Jo, who's due in October, said: "I'm feeling better now, but I've been feeling pretty sick. I've eaten for England honestly - ridiculous amounts of food!

While telling listeners she's not going to find out the sex of the baby, Jo, whose fellow Radio 1 DJ Edith Bowman is also pregnant, added: "It's a very fertile place Radio 1 - it's ridiculous!"

Expecting: Jo with husband Steve Morton and her two boys Jude and Cassius