Kate Mara is reportedly pregnant with her first child.
Page Six said Mara shared the news with friend and actress Emily Blunt at the Golden Globe Awards on Sunday.
Sources said Mara told Blunt she and Bell are thrilled to be expecting.
Mara wore an empire-waist Miu Miu gown to the Golden Globes.
"I come from a really, really big family and I've had kids around me my entire life," Mara previously told Us Weekly of being a stepmom to Jack.
"Family is everything to me and I like being surrounded by lots of kids and family at all times," she said.
"All the traveling we both have to do for work can make it hard, but we have a rule that we will never go longer than two weeks without seeing each other," she shared.
"Even if we have to spend all day traveling just to have 24 hours together, it's worth it in order to have a strong relationship."
Mara, the sister of actress Rooney Mara, is known for playing Zoe Barnes on "House of Cards" and now portrays Patty Bowes on "Pose."
Bell starred in the AMC series "Turn: Washington's Spies."