It was nearly a lifetime ago that Brooke Shields shocked the world as a knowing child prostitute in the film “Pretty Baby” and told us that nothing came between her and her Calvins.

As that rare creature who navigated her way from child stardom to a successful adult career, Shields looks back on it all as a fun time, a great opportunity. But now that she has a baby of her own, she’s wary about having her daughter follow her into the spotlight.

“I just don’t want to deny who she is naturally,” says Shields, now 39. “The business is very different now. Kids are a lot more precocious. They’re a lot more sexually aware. It wasn’t like that for me when I was a kid. We were kids. We really just were kids.”

For now, Shields is toting 17-month-old Rowan to the Broadway musical “Wonderful Town,” a project she calls the perfect complement to her new life as a mother.

Rowan watches the singing and dancing with wide eyes.

Munching on pizza backstage at the Al Hirschfeld Theatre, Shields says motherhood has made her appreciate comedy – something she fell into late in her career in the TV sitcom “Suddenly Susan.”

“I’ve just noticed that I’m OK with being happy in my work. I find that it’s just as valid if I’m having a good time. I don’t have to be suffering for it to be good or for it to be art,” she says.

Not that she doesn’t still enjoy a challenge. She had just two weeks to prepare for her role as Ruth Sherwood, a tough-talking journalist from Ohio in the Leonard Bernstein, Betty Comden and Adolph Green musical. She took over the role from Donna Murphy, who earned a Tony nomination for the part.

It was a daunting task, but for Shields, it fell into the category of the Eleanor Roosevelt adage: You must do the thing you think you cannot do. “It sort of terrified me,” Shields says, “so I basically had to say yes.”

To the world, it would seem the former model is playing against type as Ruth, a brassy, sharp-tongued woman who never gets her man. But Shields says she identifies with the old-fashioned “broad” who fends off her vulnerability with a wry sense of humor.

Audiences appreciate the comic turn and so did the critics. Her onstage battle with a stubborn sofa bed “recalls the great Lucille Ball at her most physically hilarious,” wrote Associated Press Drama Critic Michael Kuchwara, while Ben Brantley in The New York Times said Shields was “an unpretentious delight.”

“This role is so perfect for her, it really is,” says Jennifer Hope Wills, who co-stars as Ruth’s sister, Eileen. “She’s so funny, but in a natural way. And she just has that star quality.”

Wills says she grew up playing with a Brooke Shields Barbie doll and other members of the cast tried to mimic her iconic eyebrows or buy the jeans she wore. When Shields joined the cast, they were instantly endeared by her warmth and humility.

“She’s just as lovely inside as she is outside,” Wills says.

Shields is finishing a book now called “Down Came the Rain: My Journey Through Postpartum Depression,” due out in May.

She has a simple motive for speaking up: helping others get through their own personal difficulties. She’s also serving as an ambassador for the Ronald McDonald House, a charity that provides temporary housing for families of children being treated at hospitals.

“Based on the feedback I get from people when they read something … it’s been so personal and heartwarming,” she says.

The most important change for her career, Shields says, is having a child who gives her a new perspective.

“I think it makes me cognizant of wanting to be happy,” she says. “You know when you’re younger and single and an actress, there’s a kind of angst about it all. … And then when you have a child you realize that your life really begins there, and that this is all just a bonus.”

On the Net:

http://www.wonderfultownthemusical.com/