Pictured: Pregnant Jessica Alba and husband as newlyweds after last-minute marriage

The actress, who is notorious for her glum expression, was smiling at last as mingled at a charity event with her husband in tow.

Just 24 hours earlier, the pair wed at the Beverly Hills courthouse, her spokesperson has confirmed.

Newlyweds: Jessica Alba and Cash Warren attend a charity night in Beverly Hills last night after marrying in a low-key ceremony on Monday

Alba was dressed casually in a flowing blue dress and a ponytail, and sources say that aside from courthouse staff, no one else was present at the ceremony.

"She looked happy but nervous," a source told American magazine People.

Jessica, 27, is expecting a daughter with director's assistant Warren, 31, later this year.

She revealed earlier this year how they were planning a simple ceremony because she "hates" the fuss of weddings.

Smiling at last: Jessica Alba, who has a reputation for her glum expression, flashed a grin at the party

She said: "I am probably going to get my certificate at the City Council, throw a big party for the family and that's about it.

"Everyone I know hates weddings.

"I've been to very big, beautiful and romantic weddings but I would rather just throw a big party."

Her wedding was such a quiet affair that surprised even her brother, Josh Alba.

Just married: the two share a quiet laugh 24 hours after their top secret wedding

When contacted by US Weekly magazine with the news, he responded: "My sister!? I'm going to have to call her!"

The newlyweds met on the set of 'The Fantastic Four' in 2004 and got engaged in December after learning of the unplanned pregnancy.

Jessica has told how being pregnant has helped her slow down.

She said: "At the end of the day I am so tired I can't function or speak and my eyes glaze over.

"But this pregnancy has seriously mellowed me out, which is nice."