As Rooney Mara prepares to give birth to her second child with fiancé Joaquin Phoenix, the proud mom is also celebrating her birthday.

While stepping out in Los Angeles on her 39th birthday Wednesday, the Academy Award nominee dressed her baby bump in head-to-toe black.

She donned a cropped knit sweater over a matching singlet, which she tucked into elastic pants with black Nike sneakers.   

Mara revealed her pregnancy in February, when she debuted her baby bump on the red carpet of her film La Cocina's premiere at the Berlinale International Film Festival.

The Women Talking actress draped her pregnant belly in a billowing black strapless dress.

While stepping out in Los Angeles on her 39th birthday Wednesday, Rooney Mara dressed her baby bump in head-to-toe black

She donned a cropped knit sweater over a matching singlet, which she tucked into elastic pants with black Nike sneakers

She and Phoenix, 49, welcomed their first child in August 2020, a baby boy named after Joaquin's late brother River Phoenix.    

Mara opened up about motherhood to People for her first Mother's Day in 2021.    

'As a new mom, Mother's Day has taken on a special meaning this year,' she said.

'Raising our baby, River, has opened my heart to a whole new life filled with hope and more determination than ever to create a kinder and more sustainable world.'

The animal rights advocate added, 'I feel so fortunate to be able to nurture my son in all of the ways that nature intended, and I wish all mothers in the animal kingdom could experience that sacred maternal bond with their young, devoid of exploitation by humans.'

She and Phoenix will soon appear onscreen together again after they were cast in the upcoming films Polaris and The Island.

Written and directed by Lynne Ramsay, Polaris follows an ice photographer (Phoenix) who meets the Devil in 1890s Alaska. 

The couple wrapped filming on location in Alaska last year. 

The Island stars the pair as a 1930s couple who moves to a deserted island with the intention of living off the land.

Mara revealed her pregnancy in February, when she debuted her baby bump on the red carpet of her film La Cocina's premiere at the Berlinale International Film Festival

She and fiancé Joaquin Phoenix welcomed their first child in August 2020, a baby boy named after Joaquin's late brother River Phoenix

The couple will soon appear onscreen together again after they were cast in the upcoming films Polaris and The Island

Production halted on the eve of the shoot in Spain last May amid the impending Screen Actors Guild (SAG-AFTRA) strike.

After the SAG and Writers Guild of America (WGA) strikes concluded in the fall, the actors and Paweł Pawlikowski remain 'committed' to it.

Mara said at Berlinale that they 'still have hope that we will make it,' telling Deadline: 'We just don't know when that will be.' 

'It doesn't look like that will happen this year,' said Mara. 'But we're all committed to the project.'

Mara and Phoenix began dating in 2016 after starring together in 2013's Her, and they announced their engagement in 2019. 

The couple has also starred together in Don't Worry, He Won't Get Far on Foot and Mary Magdalene (both 2018).