"It's totally joyous," said Williams. "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 baby will mark Williams' second child with her husband Thomas Kail. The two are already parents to son Hart, who was born in 2020 during the coronavirus lockdowns.
"It was a reminder that life goes on," Williams told Variety. "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."
Williams, 41, is also mom to 16-year-old daughter Matilda, whom she welcomed during her relationship with the late Health Ledger.
During her interview with Variety, the Emmy winner recalled how her close friend, "Succession" star Jeremy Strong, was there for her and Matilda following Ledger's heartbreaking death from an accidental overdose in 2008.
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Williams said that after Ledger's passing, Strong, 43, moved in with her, noting that he knew how to play with Matilda, including frequent rides on his back.
She recalled, "Jeremy was serious enough to hold the weight of a child's broken heart and sensitive enough to understand how to approach her through play and games and silliness."
"[Matilda] didn't grow up with her father," Williams added, "but she grew up with her Jeremy and we were changed by his ability to play as though his life depended upon it, because hers did."
The "Brokeback Mountain" star was among the several members of Hollywood who spoke out in support of Strong in the wake of the now-infamous New Yorker profile, which painted Strong in a rather negative light while examining his approach to acting -- what he calls "identity diffusion".
While speaking with Variety, Williams again came to Strong's defense and praised his talent as an actor.
"We've all been in awe of his talent," she explained. "We've watched him work harder than anyone and wait a long time for other people to recognize it. So when he became so celebrated, we all celebrated."