So-called noms de womb can be funny, cute and just a little on the weird side.
Phoebe Payn said as soon as people discovered she was expecting twins they started to name them.
"My dad has just started calling them Jesus and Mary because they're due at Christmas," she told Helen Shield on ABC Radio Hobart.
"B1 and B2 is popular. Which is actually quite fitting because in the scan you could see them and they were actually headbutting each other like the Bananas do.
"We've been calling them Edward and Alphonse because they're the names of the lead characters of an anime we used to watch.
"We're having a lot more trouble coming up with names we might actually name them rather than the joke names."
When the question of in-utero nicknames was put out on social media, some common themes started to show.
Peanut, bean and jellybean were popular nicknames, as were Cletus the foetus and George.
And sometimes a name given to the unborn baby might be intended as their forever name — until the baby arrives.
"Fergus (the foetus), and then we thought, 'Oh actually, Fergus is a cool name'. But then when he was born we looked at him and thought, 'Oh ... you're not a Fergus'. So he got another name." — Cate Grant
Others get a nickname that turns into more than just that after the birth.
"Bean. Gave it to her as a second name." — Tim Farrell
"BB for baby boy. He still gets [called] BB, plus we picked two B names." — Toni Rugen
"Jellybean. Still her nickname at two years." — Alison Peebles
Sometimes nicknames are inspired by experiences.
"Biscuit. I ate biscuits to help with morning sickness." — Cathy Page
"Chuck, as I threw up nearly every day of the pregnancy." — Emily Jayne Ianuali
"Roo. He kicked like a kangaroo." — Wendy Reid
Nicknames can be a handy way of keeping the baby gender neutral, but sometimes it does not go to plan.
"Xena, Warrior Princess ... I thought he was a girl." — Immy Wright
And it is not just babies that can get nicknamed.
"Earl for the first [baby] and Randy for the second. And when the novelty of being called mum a million times wore off, I made them call me Boris." — Lucy Bradshaw