Conjoined twins to be separated in Calif. (pictures)

(CBS/AP) "I want them to live normally, like other children." That's what Ginady Sabuco says she hopes for her two-year-old conjoined twins, who are scheduled to be surgically separated Tuesday at a California hospital after months of planning.

PICTURES - Conjoined twins: 34 amazing photos (graphic images)

Doctors at Stanford University's Lucile Packard Children's Hospital are planning a nine-hour procedure that, if successful, will allow Angelica and Angelina Sabuco to live independently from each other.

The girls are joined at the chest and abdomen. They were born in the Philippines and live in California with their family.

Dr. Gary Hartman, a pediatric surgeon who has performed five similar procedures, said he expected the twins to do well. The operation will involve more than 20 doctors and nurses from various specialties.

The girls have done well so far. They love listening to stories and music, and they know their colors and can count to 10. They celebrated their second birthdays with cakes topped with Disney princesses and Tinker Bell.

But continuing to be conjoined poses risks to the girls' health. If one conjoined twin dies, the other will die within hours.

The girls' livers, diaphragms, breast bones, chest and abdominal wall muscles are fused. They have separate hearts, brains, kidneys, stomachs and intestines.

Worldwide, conjoined twins occur in 1 in 50,000-100,000 births. The overall survival rate is approximately 25 percent, according to the hospital.

The girls are expected to be hospitalized for nearly two weeks.