According to the University of Maryland Medical Center one in every 200,000 live twin births worldwide are conjoined, though 40 to 60 percent are stillborn and 35 percent of those who survive only live for a day.
Conjoined Twins (less commonly referred to as Siamese Twins following the birth of Chang and Eng Bunker in Siam), are genetically identical, develop from the same egg, and often share vital human organs and limbs.
Abby and Brittany Hensel are about to be the United States' most famous conjoined twins. Their lives"Abby & Brittany," will be featured in a documentary series airing Tuesday, Sept. 28 at 10 p.m. on TLC. Here's a quick look at their story, plus the stories of nine pairs who've made history around the world.