She has trouped gamely through everything from TV's Peyton Place to the Hollywood horror flick Rosemary's Baby. None of this, however, prepared Mia Farrow for the trauma of her Broadway debut. At a preview last month attended by writer Jean Kerr, her New York Times critic husband, Walter, and several other important reviewers, Mia rushed to her dressing room between acts and threw up four times. "It was the excessive strain," she says. "I envisioned this audience with Mr. and Mrs. Walter Kerr, Mr. and Mrs. Walter Kerr, row after row, all through the theater."

Pro that she is, the strain did not mar Farrow's performance—which Kerr, among other critics, valued more highly than her vehicle, Romantic Comedy. She plays a virginal schoolmarm who works with and eventually falls for a married playwright (Tony Perkins). The steady box office suggests that New York audiences like the show almost as much as Mia, who rapturously describes it as "the kind of script one dreams of receiving. It came," she notes, "at the end of a period in which I hadn't wanted to work. But I was low on funds. I was hoping something right would come along."

She had, in fact, taken nearly a year off to rusticate and read (favorites include Jane Austen and Christina Stead) on Martha's Vineyard after finishing Dino De Laurentiis' embarrassing remake of Hurricane. "I wanted to see how I felt about the major issues in my life," she says. At 34, Mia had been through a lifetime of high drama. She had a fishbowl marriage of two years to Frank Sinatra. A second try with composer-conductor André Previn ended last January—helped to its finish, reportedly, by Farrow's relationship on the Hurricane location with cinematographer Sven Nykvist. During their marriage, Farrow and Previn had twins Matthew and Sascha, 9, and Fletcher, 5; they also adopted two Vietnamese children and one Korean. "They're particularly nice kids," Farrow says of her brood. "I deeply enjoy each and everyone."

Mama Mia will soon have a seventh. She is in the process of adopting a 2-year-old physically handicapped Korean boy. (Her single status did not deter the adoption, she reports, partly because "there isn't such a demand for handicapped kids.") "I'd like to go on and adopt more children," says Farrow, who will name the new child Misha (the Russian diminutive of Michael). "I had a favorite brother, Mike, who died. I had a favorite friend, Mike, who died," Mia gently explains. Ex-husband Previn had no hand in the latest adoption but "He's for it," she says. "We're still very close, and we discussed it together." In fact, she talks by phone daily with André, who is now in his Surrey, England home with two of their six kids.

Large families are de rigueur to Mia. She is the third of seven born to the late producer-director John Farrow and actress Maureen O'Sullivan, best known as Johnny Weissmuller's Jane in the Tarzan movies. "Mia was always very strong-willed," remembers her mother. "When she was in a bad mood, we'd call that side of her personality 'Mildred.' Once, when we were on a boat going somewhere, I said: 'Let's throw Mildred overboard.' Mildred drowned, but the stubbornness remained." Observes O'Sullivan: "You know, I think Mildred is what got her through life."

Mildred plus hard work. "When I accept an acting project, I get obsessed with it," says Farrow, whose first obsession came at age 17. Directly out of her London finishing school, she was cast in an off-Broadway production of The Importance of Being Earnest. A year later she was a household heroine as the love child Allison MacKenzie in Peyton Place. Film stardom followed, with Rosemary's Baby and The Great Gatsby. Farrow almost always played the fragile ingenue, a persona that has earned her the label "vulnerable," which she disputes. "I'm really very strong," she insists.

Despite her protests, Farrow has shown a certain eagerness to please over the years. At a tender 19, she struggled to fit into the Hollywood Ratpack of husband Sinatra (30 years her senior). "A lot of good things came out of it," she says now of that four-year liaison. "It wasn't a failure in my mind." During one of their separations, Farrow flew off to India to meditate with the Maharishi Mahesh Yogi. "I went, my dear, to the Himalayas to be alone," she says with a dramatic flourish. "Then the Beatles arrived. There were photographers hanging from the trees. I had to leave."

The more mature Mia now seeks fulfillment in her children. During the run of Romantic Comedy (she is committed for one year), Farrow hurries home to her rented apartment to tuck in the kids every night. Hoping they will absorb their father's passion for music, she beds them down with tapes of the classics. "They choose the composer," says Farrow. "One night last summer, Matthew wanted Haydn and Sascha wanted Shostakovich. He said Shostakovich was better to jump to."

Refereeing such sibling conflicts keeps Farrow's social life to a minimum. "I don't think she wants a man in her life right now," says her mother. But there have been stories of a rematch with Previn. "We have a strong bond between us" is Farrow's guarded response. "Though I often tell him," she adds, with an impish smile, " 'Why mess around with a woman with seven children?' "