The American Pediatric Surgical Association says that conjoined twins take place in one out of every 50,000 to 100,000 births. When compared to identical twinning's frequency rate of four in every 1,000, conjoined twins remain a relative medical rarity.
Allison and Amelia Tucker were born joined at the chest and abdomen. Doctors advised their parents to terminate the pregnancy. The Tuckers decided to carry through and when the girls were born, surgeons decided that they might be able to separate the twins.
So when the girls were only 8 months old, surgeons did just that in a hours-long procedure involving scores of specialists.
Watch the incredible video from ABC News below: