Jessica Alba. Picture: Supplied

Jessica Alba is pregnant with her third child.

The 'Sin City: A Dame To Kill For' star and her husband Cash Warren are set to add to their family with a new baby on the way.

Revealing the news on her Instagram account, Jessica posted a cute video of her daughters - Honor, nine, and Haven, five - holding big number one and two balloons, with the actress holding one that read number three as she displayed a visible baby bump.

She captioned it: "@cash_warren and I are officially going to be outnumbered #babyonboard #herewegoagain #blessed (sic)"

Jessica is incredibly close to her daughters and regularly takes them with her to work with her to ensure she is never away from them for too long.

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She explained: "I go on so many business trips, and they're usually two to three days. I'll bring just one at a time and it'll be like, 'Mom's gonna bring you on a special trip. We'll get to have a sleepover, we'll get to order room service, we'll get to rent a movie. It's really fun!

"I just try to make the time that I spend with them quality. We like to go on walks and we like to watch movies and barbecue. They love to take a bath and then get back in their pyjamas for the rest of the weekend.

"Honor is reading a series called 'Amulet'. We finished 'Beezus and Ramona'. Haven loves 'Cat in the Hat' and 'Green Eggs and Ham' because I do silly voices. There's also 'Freckleface Strawberry', Julianne Moore's book. She likes funky, funny characters."

And the Hollywood star previously revealed being pregnant helped her learn to "respect" her body.

She shared: "It's incredible being a mom, I love it. I was much more stressed and concerned about my body before I had kids. But now I know how silly and unimportant it is, so it's certainly given me perspective. Being pregnant and giving birth gave me a new found respect for my body, it's amazing."

Bang Showbiz