The 34-year-old is in California to make a return appearance on Dancing With The Stars – the US reality show she competed on in 2012. She was dressed fittingly for the rehearsals in black leggings and a loose fitting vest, along with a pair of low-heeled dancing shoes.
Katherine later shared a photo from the rehearsals on Twitter, alongside her "bestie" from the show, American journalist Maria Menounos.
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Katherine Jenkins kept her baby bump hidden in LA on Monday
"With my beautiful #DWTS Bestie @mariamenounos #DWTS20 So happy to be back!" she wrote.
The opera singer's appearance in Hollywood comes just a week after she announced that she is expecting a baby girl with her husband Andrew Levitas. Katherine revealed the happy news on Instagram, with an adorable snap that showed a pair of pink baby slippers resting on a framed black and white portrait from her wedding.
"Couldn't be more excited to meet our little girl! #MummyToBe #DaddyToBe #ArtProject #Collaboration #Family @Andrewlevitas," she wrote.
Katherine's husband Andrew also shared the news on his own Instagram account at the same time, and both were inundated with congratulatory messages on the social media site.
It will be the first child for both Katherine and Andrew, and the Welsh star is understandably overjoyed after recently revealing that she was ready to start a family.
"I can't wait to have kids," she told HELLO! magazine in November. "I can't wait for us to become a family if and when – God willing – that happens."
Katherine and Andrew tied the knot at Hampton Court Palace in September. The couple first went public with their relationship in March 2014 when Andrew accompanied the singer to Buckingham Palace to collect her OBE.