PHILADELPHIA (AP) — Surgeons at a Philadelphia hospital were scheduled to operate Wednesday to separate 8-month-old twins from New York joined at the lower chest and abdomen.

Allison and Amelia Tucker of Adams, N.Y., share their chest wall, diaphragm, pericardium and liver, Children’s Hospital of Philadelphia said. The girls are “excellent candidates for separation,” lead surgeon Holly Hedrick said in a statement.

Hedrick said doctors expect that after the surgery and a period of recovery and therapy, the girls “will be able to live full, healthy and independent lives.”

Officials said the surgery will be the 21st separation of conjoined twins performed at the hospital.

Conjoined twins occur once in every 50,000 to 60,000 births, and most are stillborn. About three-quarters of such twins are female and are joined at least partially in the chest, sharing organs. Chances of successful surgery and survival are greater if the twins have separate sets of organs, the hospital said.

A year ago, conjoined 20-month-old twins from the Dominican Republic were separated at a Virginia hospital. Maria and Teresa Tapia were attached at the lower chest, and surgical teams successfully divided their liver, pancreas and other shared organ systems and reconstructed their abdominal walls.

A few days before that, 2-year-old twin sisters Angelica and Angelina Sabuco from San Jose, Calif., who were joined at the chest and abdomen, were separated in procedures performed at a California hospital.

(© Copyright 2012 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)