Pediatric surgeon Dr. Holly Hedrick says Allison is the smaller but tougher twin. Amelia is the larger twin but she's still in intensive care for now.On November 7th , a 40-person surgical team performed the separation surgery that lasted seven hours. "Gregg and I are thrilled that our daughters have been given this remarkable gift by the amazing team from the Childrenâ??s Hospital of Philadelphia," says Shellie Tucker. "We are so grateful for the support and encouragement that the medical team, our family, and our friends have given us during this long journey." The couple first learned that Shellie was carrying conjoined twins 20 weeks into her pregnancy. They were referred to CHOP Center for Fetal Diagnosis and Treatment where it was determined that the Tucker twins were excellent candidates for separation. This is the 21st such separation performed at the hospital. Conjoined twins occur in one in 50,000-60,000 births, most of which are stillborn, according to CHOP, and about 75% are female.