Giggling, Charlie asked if Greg wanted to see her belly, and he cried: "Oh my God! What?"
"Surprise!" she yelled.
Viewers were thoroughly tickled by Greg's shock.
"The conversation and announcement between @charliehedges @gregjames was the best!" one person tweeted.
"Huge congratulations and what a way to reveal the news," said another.
One fan posted: "@charliehedges just casually dropping big news during 'tell me something good'. Congratulations Charlie!
"I loved @gregjames' reaction. I think he was as shocked as everyone else was!"
"I think the best part of that announcement was you being so shocked," another said to Greg.
Charlie – who presents as part of Rickie, Melvin and Charlie – later shared a picture of her sonogram on Instagram emblazoned with the words: "Hello everyone. I'm baby Hedges, it is so nice to meet you all. See you in person very soon."
She wrote in the caption: "I am so incredibly grateful and excited to be sharing the most beautiful news with you all … I am going to be a new mummy very soon and Baby hedges would like to say hi to you all.
"To say we are over the moon is an understatement xxx."
"Meant the world being able to share this blessing with my Radio 1 family and all of you today," Charlie added in another message.
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