Michelle Williams Walks First Red Carpet Since Welcoming Third Baby

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Michelle Williams is back in black.

The mom-of-three, 42, hit the red carpet Sunday just weeks after giving birth to her third baby in support of The Fabelmans film, which premiered at the AFI fest in Los Angeles.

Wearing CELINE by Hedi Slimane in a strapless black satin gown, Williams opened up about the family bond the cast and crew developed on the set of the Steven Spielberg movie, which revolves around the legendary director's real-life family.

"We love each other a lot," Williams tells PEOPLE about the process of stepping into the role of Mitzi, a character that's largely based on Spielberg's late mother Leah Adler. The movie also stars Seth Rogan, Gabriel LaBelle, Paul Dano and Judd Hirsch.

"I think seeing how connected he is to his childhood is really inspiring," she adds of Spielberg. "That's a place that he continues to draw from."

Childhood is also something that's firmly at the forefront of Williams' mind following the birth of her second baby with husband Thomas Kail.

"I think about the present moment probably more than about what's to come," she tells PEOPLE when asked about her own legacy. "Whatever you lay in the present moment becomes the past, so that's what I'm most keenly attuned to right now."

RELATED: Michelle Williams and Husband Thomas Kail Welcome Second Baby Together

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RELATED: Michelle Williams and Thomas Kail's Relationship Timeline

Williams and Kail met when she starred in the award-winning 2018 miniseries Fosse/Verdon, which Kail executive produced and directed several episodes of. The couple didn't get together right away, however. At the time, Williams was still married to musician Phil Elverum, and Kail was with his ex-wife Angela Christian.

After a whirlwind romance, they welcomed their first son together, Hart, now 2, and got engaged within a year. They have now been married since 2020. Their family of five also includes Williams' teenage daughter with the late Heath Ledger, Matilda Ledger, 17.

The actress was photographed last week walking with a newborn baby cradled against her chest as she and her husband Thomas Kail went for a stroll in New York City. Reps for the couple did not comment on the news.

Williams first revealed news of her third pregnancy to Variety in May.

"It's totally joyous. As the years go on, you sort of wonder what they might hold for you or not hold for you. It's exciting to discover that something you want again and again, is available one more time. That good fortune is not lost on me or my family," The Greatest Showman actress shared.

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Speaking about becoming a mom again during the pandemic, Williams said, "It was a reminder that life goes on. The world we brought a baby into is not the world we thought we were bringing a baby into, but the baby is ignorant of that. He experiences the unmitigated joy of discovery and the happiness of a loving home."

"There's nothing that makes you committed to a better world than raising a great kid. It's the ultimate creative act," she added. "The most ecstatic moments of life and art are the transcendent ones. Having children is like that. You combine your DNA with someone else to create a new life."