But it was the emergence of the feminist movement of the 1970s, when women pushed for reproductive freedom, that gave women more control of their bodies, Rupp said.
"Now there are more options for women, and it's more socially acceptable," Rupp told ABCNews.com. "But it's not just about biology."
There are numerous examples of prominent women who came out publicly after years of living heterosexual lifestyles.
In 2004, "Sex and the City" actress Cynthia Nixon left her boyfriend of 15 years and their two children and began seeing a female public school advocate, whom she'd met while working on a campaign to reduce class sizes in New York City.
"I have been with men all my life and had never met a woman I had fallen in love with before," Nixon told the London Daily Mirror. "But when I did, it didn't seem so strange. It didn't change who I am. I'm just a woman who fell in love with a woman."
Novelist and social critic Susan Sontag remained in the closet until her longtime lover, photographer Annie Leibovitz, outed her posthumously. Sontag, who had been married and had a son, died of cancer in 2004 at the age of 71. She had been in a romantic relationship with Leibovitz, now 59, since 1989.
But even with the increased social acceptance, there are challenges.
One New York City therapist who came out at 43, after she'd been married and had three children, worried that publicity would hinder her work with patients.
"Also, my children -- now married with children -- and I have finally resolved issues and are enjoying a comfortable and quite wonderful relationship, and I don't wish to interfere in any way with this," the woman, who asked to remain anonymous, told ABCNews.com.
Another, a New Hampshire school principal, was concerned about her 27-year-old daughter and 23-year-old son.
"I don't want my children to read what I'd say in relation to their father," said the 56-year-old lesbian. "I've spent a lot of time trying to fix that relationship, and I don't want to do any harm."
"Phoebe," a 60-year-old Connecticut children's librarian, said she, too, was concerned about talking openly about her civil union. She left a happy, 23-year marriage with three children, now 32, 30 and 28.
"I never had the faintest, tiniest inkling that I was gay," said Phoebe, who asked that her real name not be used. "It never entered my mind. If it had, it was as likely as thinking I was an ax-murderer."
Phoebe told ABCNews.com that from a young age she had been groomed by her mother for marriage and children.
"Everything was couched in who I would marry, not who I'd be," she said. "If I was interested in medicine, she'd say, 'One day you'll marry a doctor.'
"I was a good girl, so it was important to me to be good, and also I didn't have a sense of who I was as a person," said Phoebe.
In retrospect, she remembered being attracted to another girl at 9. "I had never had a crush like that on a male. But I suppressed it."
At 20, Phoebe married and had a child, then divorced and remarried a minister. She had a rich marriage and two more children.
By chance, as Phoebe approached 50, she met her partner though the church, a woman 15 years her junior.
"There was a total attraction, and we were getting close spiritually. I didn't know it would happen, but by the time it dawned on me, it was too late," she said.
Like many women, Phoebe said she fell in love first.