What they saw in CT scan images stunned them.
"We were just flabbergasted," Womble recalled.
The X-Ray images showed Cotton had an IUD - an intrauterine device designed to prevent pregnancy - in her body. Until that moment, Cotton never knew it was there.
The sisters began tracing back through Cotton's medical history, and realized the device had been implanted some 40 years before without her permission.
"It was something forced on her without her consent and I equate that as a woman being raped. It's something against her wishes," offered Womble - a professor at NC Central University.
Cotton was 21 in 1967 when she gave birth to her third child at the Mathiesen Clinic in Pittsboro, NC. According to the birth certificate, Dr. K.M. Mathiesen delivered the baby boy.
Womble said her brother-in-law recalled having a heated conversation with Dr. Mathiesen.
"The last thing he heard was 'You-all don't need to have any more children,'" said Womble. "He had to have inserted it right there because she was still in the hospital."
That a doctor could take it upon himself to secretly prevent a woman from having more children is not surprising to Dr. Eric Juengst with the UNC Center for Biomedical Ethics.
"This sort of surreptitious sterilization or implantation of contraceptives was done," he explained.
In 1967, North Carolina was at the height of its eugenics movement. According to the state's own records, the Eugenics Board ordered women as young as 10 sterilized for offenses as minor as not getting along with schoolmates, being promiscuous or running afoul of local social workers or doctors.
North Carolina wasn't alone. Nationwide, there were more than 60,000 known victims of sterilization programs, with perhaps another 40,000 sterilized through "unofficial" channels like hospitals or local health departments working on their own initiative.
North Carolina records reflect it officially sterilized some 7,600 people between 1929 and 1974.
"These decisions were made disproportionally for poor, people of color, uneducated, the marginalized parts of the societies," said Juengst.
Eugenics was aimed at creating a "better society" by filtering out people considered undesirable, ranging from criminals to those imprecisely designated as "feeble-minded."
North Carolina officially ended the sterilization program in 1977, three years after the last procedure. In 2002, then-Gov. Mike Easley apologized for the program. Just last month, a governor's task force on eugenics released its final report and recommended paying $50,000 to each living victim. The issue now goes to the General Assembly for action.
Womble told ABC11 what happened to her sister was a reflection of the times.
"It was an era where blacks were ill treated," she said. "The 60s is when the riots were going on, the blacks were protesting, we were trying to get our equal rights."
While Cotton's case was not part of the official eugenics program, Juengst told ABC11 he finds it just as disturbing.
"It's particularly problematic from a moral point of view. Not just for the moral, [there are] ethical reasons that you shouldn't do things to patients without their consent," he said. "Legally, this was battery, essentially unconsented touching, and that applies to the practice of medicine as well as to people on the street."
"Battery is a very strong word and I think that is the correct word to use for her and for this situation," she said. "It was just like taking an animal and doing something to the animal that couldn't fight back. It was horrible."
Womble said her sister has no doubt Dr. Mathiesen was the doctor responsible.
"She's certain about that because she went to no other doctors. She's never been sick, we didn't get physical checkups back then," she explained.
Dr. Mathiesen's side of the story is not available. He died in 1999.
According to old newspaper articles, the Mathiesen Clinic in the heart of Pittsboro opened in 1949 and closed in the 1970s. Mathiesen's old medical partner told ABC11 the clinic did implant IUDs in the 1960s, but only with the patient's consent.
He told us Mathiesen was a good doctor and a compassionate man. Some long-time Pittsboro residents agree.
"He was the only person who could give medical attention to anyone at the time - black or white," offered Kevin Sanders who remembers the clinic where he was born.
"My grandmother still speaks so highly of him, and she's going on 93," he said.
But Womble and her sister have a different view of the late doctor.
"I don't know the man personally, so I hate to make a judgment about his character. I just know what was done to my sister," said Womble.
Cotton had the IUD surgically removed and the pain in her stomach went away. The 40-year mystery about why she never had any more children was solved.
"I think there is a lot of sadness with it. It's a sadness when I reach back and see how she longed for children," said Womble.
Womble told ABC11 she doesn't believe her sister was the only woman who had an IUD implanted against her will. She'd like to know if there are more victims out there.
If you know of someone who had a similar experience, contact the I-Team at email@example.com.