Actress Jessica Alba stepped out with her huge baby bump last night in an unflattering, transparent maternity gown.

The Fantastic Four beauty, who celebrated her 27th birthday on Monday, showed off rather too much of her rapidly changing figure as she dined out in LA last night.

Jessica and her director's assistant fiancé Cash Warren, 29, are expecting a baby girl in early June.

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Mummy to be: Jessica Alba steps out in an unflattering see-through dress at a Beverly Hills restaurant last night

Just four weeks ahead of the baby's arrival, the couple dined out at celebrity hangout Mr Chow in Beverly Hills.

Despite spending most of her pregnancy in a variety of flattering outfits, Jessica made a fashion faux pas on Wednesday with her all-black clingy ensemble.

Instead of her usual colourful, stylish outfits, Jessica combined a sheer black dress with a baggy cardigan, black tights and loafers.

The clingy dress struggled to contain Jessica's ample cleavage and the actress' lack of bra support left little to the imagination.

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Buckle up: The tired couple head home after an early dinner at Mr Chow

Despite her maternity fashion mistake, Jessica has been voted sexiest woman in the world by the Australian edition of FHM magazine.

That's more like it: A glowing Jessica Alba in a stunning Marchesa gown at the Oscars earlier this year

After appearing in a trio of recent movies, Jessica is taking time off acting to be a full-time mother.

She has spent the last few weeks decorating the couple's new house in Beverly Hills.

At a book launch last month, Jessica admitted: "I'm just trying to get my house ready before the baby comes.

"It's kind of hectic, it's getting close and the house isn't even ready yet.

"I'm used to having to be somewhere all the time, and it's kind of the first time in my life where I really haven't been working in a while, and now it's just about the baby being healthy, the house being ready, and nesting, it's really different."

Jessica and Cash started dating in autumn 2004 after meeting on the set of the Fantastic Four, where Cash was working as a director's assistant.

The couple were reported to have briefly split last July, but reunited the following month.

They announced Alba's pregnancy and their engagement in December, and purchased their first home together weeks later.