"In the 1950s when adoption was more popular, they wanted to hide the shame of the illegitimate family and the adoptive family didn't want interference in creating the perfect family," she said. "The adoptive birth certificate should reflect the new person."
In 1960, the laws in 40 percent of the states still permitted adult adoptees to inspect them, but between then and 1990, all but a handful of the rest of the states closed the birth records to adult adoptees.
When mores changed, a generation of adoptees began searching for their birth parents, and adoptive parents felt threatened that their children wouldn't love them, according to Samuels.
The focus of protection shifted away from the birth mother and her child to the rights of adoptive families. Efforts to keep records closed were led by adoption agencies, attorneys general and legislators, but not by the birth mothers themselves.
Today's adoptive parents are more apt to fight for the "rights of the child and their origin," said Samuels. And birth mothers are speaking out.
In 1979, Mary Lou Cullen gave up a son in a closed adoption when she was just 19, never telling a soul, not even her husband or later three children. She was contacted by her birth son Nathan, who is now 30, by letter eight years ago.
"He said, 'If you don't want any communication, that's fine, but if you do, this is how you can get a hold of me.' I never even second guessed or had a moment of hesitation, knowing I was going to contact him," said the Marshfield, Massachusetts, mother of three more children. "But I had a whole lot of people to tell."
The reunion and revealing her secret was "stressful," said Cullen, who is now president of Concerned United Birthparents. But after working it out, birth mother and birth son have become close.
Even though both Nathan's adoptive parents and birth parents supported the reunion, he can still not access his birth certificate in Ohio, where he was born.
"Once Nathan met me and my family, he said he felt like it completed him," said Cullen, now 50. "For me, it was very difficult for a number of years, but it's my truth and I don't need to deny it anymore or hide it or cover it up. I can live my honest truth."
"On top of that, I got to meet my first born, who I never thought I would see again," she said. "I had no idea what had happened to him. And I was able to deal with the grief that I had never dealt with before."
But Jean Strauss, a filmmaker who for 30 years has has chronicled the lives of adult adoptees in books and documentaries, admits, "It's not all about reunions."
Her film on adult adoptees searching for their identities, "For the Life of Me," premiered at the Cleveland International Film Festival in March.
"Owning your own information is a very powerful thing," said the now mother of two. "You are a human being and this belongs to you."
Born Cecelia Ann Porter in California in 1955, where records are still sealed, Strauss hired a private investigator to find her birth mother after her beloved adoptive mother died in 1988.
"I was terrified I might hurt her," said Strauss, who described her adoptive mother as "my best friend."
When they reunited, Strauss was 33 and her birth mother Lee Beno was 54. Six years later, they located Beno's 80-year-old birth mother, Mary Miklosey, who had grown up in an orphanage where she had been sent when her own mother died.