Watch: Alex Jones makes hilarious baby slip up on The One Show
The One Show presenter - who competed in Strictly in 2011 - revealed the awkward mistake she made after "skim-reading" social media, when the professional dancing couple appeared on the BBC show together.
Jones admitted: "Last week, all I saw - because I sort of skim-read - was 'baby news, Aljaž and Janette!' and I was like: 'Oh they're having a baby, that's lovely news.' But you're not having a baby, they tell me?"
She added: "I sent a little message saying congratulations, which would have been okay as it still makes sense with the sister… But I was like: 'Oh my God, is Janette going to do Strictly? How will it work?'
"I was way ahead - slightly awkward!"
Skorjanec explained: "No, my little sister gave birth to a beautiful little niece so that's the baby news."
The 30-year-old dancer had posted on Instagram a picture of a newborn baby's hand, captioned: "I am a UNCLE! Again!"
But Manrara, 32, admitted she and Skorjanec do hope to start a family together.
She told Jones: "We always wanted to have a baby, but 2020 has definitely made me say to myself: 'You know what, Janette, it's never going to be the perfect time but it's always going to be the right time'.
"As a woman who's a dancer, my body is my job so it's scary to make that decision about the perfect time to start a family.
"I always thought there would be a perfect month and year, but what 2020 has made me realise is that perfect time is never going to come along."
Watch: Maintain a positive mindset with this ballet-based workout