Conjoined twins: Allison and Amelia

Eight-month-old conjoined twins Allison June and Amelia Lee Tucker from Adams, N.Y., were successfully separated on Nov. 7, 2012, at the Children's Hospital of Philadelphia.

The Tucker family poses for a portrait with the now-separated twins. "Greg and I are thrilled that our daughters have been given this remarkable gift by the amazing team from The Children's Hospital of Philadelphia," said Shellie Tucker, the twins

The Children's Hospital of Philadelphia video

According to the University of Maryland Medical Center, conjoined twins occur about once every 200,000 live births and can be documented back to at least 1100 when two twin girls, Mary and Eliza Chulkhurst from Kent, England, were born joined at the hip. Conjoined twins used to be called Siamese twins because of a famous pair in 1811 named Eng and Chang Bunker from Thailand, which was called Siam at the time, but the term is no longer used. An X-Ray of Allison and Amelia shows where the twins were joined.

Eight-month-olds Allison June and Amelia Lee Tucker were joined at the lower chest and abdomen. The two sisters shared a chest wall, diaphragm, pericardium and liver. The two girls have an omphalopagus connection, which accounts for 33 percent of all conjoined twins, according to the University of Maryland Medical Center.

Greg Tucker looks over his daughters in a tender moment.

Doctors at The Children's Hospital of Philadelphia work to separate Allison June and Amelia Lee Tucker, on Nov. 7, 2012 in Philadelphia, Penn. It took Dr. Holly L. Hedrick, a pediatric general, thoracic and fetal surgeon, and about 40 other medical professionals approximately seven hours to separate the girls and complete the necessary reconstructive surgery. This is the 21st case of separating conjoined twins for the hospital. "Like all separations of conjoined twins, this was a very complex surgery, but it went very well and as expected," Hedrick said in a press release.

Parents Shellie and Greg Tucker look at one of their daughters post-operation.

The two girls are nearly 10 months old now and are enjoying each other company. "Both Allison and Amelia are doing well, and we expect them both to enjoy full, healthy and independent lives," Hedrick said in a press release.

Shellie Tucker (holding Allison), Greg Tucker (holding Amelia) and their 2 1/2-year-old son Owen pose with some of the twin's doctors at a press conference about the twin's successful separation, Dec. 20, 2012.

Shellie Tucker, holding Allison, and Greg Tucker, holding Amelia, pose on Dec. 20, 2012, at the Children's Hospital of Philadelphia.

Allison Tucker poses for the camera during a press conference about her separation surgery, Dec. 20, 2012, at the Children's Hospital of Philadelphia.

The Tucker family poses with the surgical staff from the Children's Hospital of Philadelphia who helped separate the twins.