Isiolo, Kenya (CNN) -- "Josephine" is 12 years old and several months pregnant.

She's a member of the Samburu tribe, living in a small village in a remote part of Isiolo in Kenya's Eastern Province. The pre-teen, whose identity is being protected, claims she had sex with a relative -- a rape sanctioned by the Samburu, through a practice called "beading."

Intricate beaded necklaces are a symbol of the Kenyan nation. But to young Samburu girls, the necklaces are a symbol not of national pride, but something much darker, that can lead to rape, unwanted pregnancies -- and even the deaths of newborns, according to activist Josephine Kulea and the Samburu tribe itself.

In "beading," a close family relative will approach a girl's parents with red Samburu beads and place the necklace around the girl's neck.

"Effectively he has booked her," says Kulea, a member of the Samburu herself. "It is like a (temporary) engagement, and he can then have sex with her." Girls are also "beaded" as an early marriage promise by non-relatives.

Some girls who are "beaded" are no more than 6 years old. They are the focus of Kulea's rescue mission, a trip to Isiolo she's been planning for weeks.

Samburu culture dictates that girls be engaged to a relative, she says, and they are allowed to have sex with him. But "they are not allowed to get pregnant and there is no preventative measures," she says. "At the end of the day, most girls get pregnant ... and these (infants) end up dying or being killed or being given away."

When they reach adulthood, Samburu girls will marry outside of their village, but taboo dictates the girls will never be able to marry if they keep their babies resulting from beading.

Some girls, she says, undergo a crude abortion before their pregnancy advances. Others hide their condition until it is too late for that. "They let them give birth, but only to kill these babies," Kulea says.

If the girls are lucky, their babies are given away to strangers. "Most of these girls are traumatized," Kulea says, and some get infections from the crude abortions.

Philip Lemantile, the father of 14-year-old Nasuto, says beading is aimed at stopping promiscuity among young girls.

"This is our culture," he says. "It is part of us. And we have been practicing it, and we accept that these girls should be beaded, and sometimes the girls just get pregnant."

Kulea calls that a bad cultural practice.

"For any change that comes by, we have to have a start," she says. "And this is the start."

But the start is traumatic for the Samburu, as the girls are taken away from their families and put in a shelter. Their babies are placed in orphanages.

Still, Kulea says, it's better than staying.

"I just felt that it is wrong," she says. "Something wrong is going on in my community. And that is where my passion began. And so I decided to help out the girls."

Journalist Lillian Leposo contributed to this report.