They can produce phony sonograms and use pads in their clothing to appear pregnant. When they are convicted, they tell stories about infertility and miscarriage and "engender a lot of sympathy."
Pettway, the woman whom White called mom, reportedly lost a baby before the abduction.
"They don't plan for what to do after the baby goes home and they show it to the boyfriend and live happily ever after," he said. "Most women take care of them and love them, but it's not always true. The guy may hang around for a year or two but not long term."
The majority of these women are usually caught quickly when a neighbor reports that a woman suddenly showed up at the supermarket with a baby.
Those who are most successful, as in the Carina White case, leave the town or state where the kidnapping happened.
"The further away you go, the better the chance that you get away with the crime," he said.
Sentences can vary depending on the case.
Federal law does not distinguish between kidnapping cases: "It's kidnapping whether it's a birth or death," Lanning said. "There is no major difference in the eyes of the law. It's a gray area to what extent there is consent."
Some cases involve the actual cutting out of the fetus by a crude Caesarian section, according to Jack Levin, professor of sociology and criminology at Northeastern University in Boston.
"These sociopathic women will literally snatch an unborn child from a mother's abdomen in the ninth month of pregnancy," Levin said. "They are the smallest minority. You really have to be awfully desperate to kill the mother to get the child and to do it hands-on in such a gory manner. Most people are incapable of that."
Most are not intending to hurt the mother, Levin said. "She rationalizes that the biological mother can have another baby and she can't. She has a conscience, but has a complex rationalization that she can use to justify this criminal act."
As for Carlina White, Levin said that because the kidnapper took the girl 23 years ago without being detected, that means police have a wealth of information from the home. White can also identify the woman who claimed to be her mother.
"I am not sure where police will start," he said. "They have already started and I am sure it began with the daughter and the home she was raised in."
Levin said the public will likely be involved as soon as people learn "what the woman looks like and her personal habits."
"They probably know where to look," he said. "There will be a public display of her photo and information about her lifestyle that will ultimately bring her to justice.
"It shouldn't be very difficult. She is clever but she should be easy to apprehend. I'd be shocked if she stayed on the loose very long."