The actress, who is currently in New Zealand, joked about not being able to escape lockdowns on her Instagram story. It appears from the timing of her post she managed to sneak in a celebration for her baby over the weekend before Auckland went into Covid-19 alert level 3.
The actress elected not to share her due date with the Herald at this time.
In Janauary, the star married her partner Donny Grahamer in New York. She shared beautiful photos of the couple together, with Castle-Hughes donning a floor-length floral dress.
The 30-year-old star has one child she shares with her ex-boyfriend Bradley Hull, a daughter named Felicity who was born in 2007. Castle-Hughes was 17 at the time.
She was previously married to Jonathan Morrison, but they divorced in 2016 after marrying on Valentine's Day in 2013.
Her recent notable acting roles include her role as Special Agent Hana Gibson in the TV show FBI Most: Wanted, plus Obara Sand in Game of Thrones.
She was nominated for an Academy Award for her role as Paikea in The Whale Rider, an incredible feat for the then 13-year-old who had no prior acting experience. She was just 11 when she starred in the movie.
In 2018, she reflected on the experience in an interview with Australian presenter Marc Fennell.
"I was thrown into it at such an intense level. I shot the film when I was 11, and I was at the Oscars at 13. I felt really disassociated from myself. People were always like, 'This is it! You must be so excited!' I'd be like, 'I'm excited because everyone else is excited, but I don't really know what this means.' There was a huge part of me that just wanted to go home and be 13 and go to school and kiss a boy," she said at the time.