File photo: Meanwhile, Jessica previously revealed her third child will be her last. Picture: AP

Jessica Alba is expecting a baby boy. The Sin City: A Dame To Kill For star took to social media to reveal her and her husband Cash Warren - who are already proud parents to daughters Honor, nine, and Haven, six - are expecting their first son together.

Alongside a video of the big reveal, Jessica wrote: "@cash_warren and I couldn’t be more thrilled to announce... #officiallyoutnumbered #babyboy #cantwaittospoilhim #hugsandkissesforlife #soontobemamaofthree (sic)"

In the short Boomerang video, Jessica can be seen standing with her daughters, who tug on a string that releases a whole host of blue confetti from an Honest Company box onto them.

Meanwhile, Jessica previously revealed her third child will be her last. When asked if she wanted to add to her brood again once her son is born, she laughed as she insisted this was the "last one".

And Jessica works hard to balance her family life with her work commitments. Explaining how she does it, she shared: "I think it's the quality of time that you put in at work and how you're fed at work and what you bring home. And also what you let go of when you come home.

"A happy work place actually makes for a healthier person and healthier children. If you work five hours a day but you hate your job, your attitude when you come home and what that imposes on your kids outlook and their life and their relationship with them, it actually really affects it.

"But if you're happy - even if you come home late and you're working long hours - if they see that you're happy and you're in a good mood and you're present with them that's way better than you spending ten hours a day with them in misery."