Born within a year of each other, the Carlsen and Fitterer twins are just like any active 8- to 9-year-old girls, but, more than eight years ago, the North Dakota natives defied the odds.
Both Abbigail and Isabelle Carlsen, and Abygail and Madysen Fitterer were born conjoined.
"I was more in shock and scared," said Amy Carlsen, Abbigail and Isabelle Carlsen's mother. "When you first hear that, you don't believe it; you're in denial."
Conjoined twins occur once in every 200,000 live births. About 40 to 60 percent of conjoined twins are stillborn with another 35 percent that survive one day, according to the University of Maryland Medical Center.
The Carlsen and Fitterer girls are the only conjoined twins from North Dakota to be separated.
The Carlsen twins, 9, were born on Nov. 29, 2005, joined from the mid-chest to their naval and shared parts of their liver and small intestine, as well as part of the portal vein, through which oxygen-depleted blood flows to the liver.
Sharing the portal vein meant that Abbigail Carlsen was stealing nutrients from her sister and gaining more weight, said Jesse Carlsen, the twins' father.
Isabelle Carlsen also had about one-third of her heart inside of her sister's chest. After their separation surgery, Isabelle Carlsen was left with nothing but skin and no sternum to protect her heart.
The Carlsen twins were separated at 5 and a half months, in 2006, without any major complications except for short-term withdrawal symptoms from pain medication.
Similarly, the Fitterer twins, 8, were also born joined from the chest to the middle of their abdomen on Aug. 8, 2006.
They shared one liver that had two drainage systems, and Abygail Fitterer had a quarter of her heart inside Madysen Fitterer's chest. The Fitterers were separated in the beginning of 2007.
Both families are pursuing a more ordinary life with their children.
"We kind of let them be normal kids," said Stacy Fitterer, father of Abygail and Madysen.
Abbygail and Madysen Fitterer are crazy little artists, their mother, Suzy Fitterer said, and they enjoy being active, playing outside and swimming.
"There's nobody who can beat them on the monkey bars," she said. "They are very physical little girls."
Despite being shy, Suzy Fitterer said, the girls are very intuitive to other kids with disabilities.
Isabelle and Abbigail Carlsen, though similar, have developed different personalities.
Isabelle, who prefers to be called Belle, likes to play piano, facepaint and go ice skating.
Abbigail enjoys drawing, she's donated her hair to Locks of Love, and everyone at school refers to her as Abby the Queen.
"I'm not normal," she said. "I'm beautiful."
Both girls play soccer and have been doing gymnastics since they were 2, and they are currently at the level of NOVA Stars at Dakota Star in Mandan.
Jesse Carlsen said that, despite the differences in personality, the girls are still very close.
"They just don't like to admit it," he said.
Amy Carlsen said there are certain things they do without realizing it.
"When they're singing in a concert or they're near each other, they hold hands," she said.
When they're not together, she said their hands search for the other and they've always been aware of their separation.
The Carlsens used mirrors by their beds when the girls were first separated, so they wouldn't know they were alone and, when one would cry, the other's heart rate would go up.
"You just knew they were stressed and then, when they were brought back together, they were calm," she said.
The Fitterers used dolls for their girls to sleep with after their surgery because they were always looking for each other.
Although the parents try to make their lives as normal as possible, there are concerns and things that need work.
After the surgery, neither set of twins had any core strength because of where they were conjoined, which required physical therapy.
"When they first started gymnastics, you could tell how much weaker they were," Amy Carlsen said. "It keeps them aligned."
Chest protection was also a major concern for the girls because Abygail and Madysen Fitterer and Isabelle Carlsen didn't have anything protecting their hearts.
The girls had to wear chest protectors, and Isabelle Carlsen had a surgery about two years ago to place Gore-tex patch in her chest.
Overall, the Carlsen twins have been in good health, according to Amy Carlsen, who said they haven't needed to go back to Mayo Clinic in Rochester, Minn., for a checkup since the heart surgery.
"You would never know," she said. "All children are miracles, but they're the miracles here."
Abygail Fitterer missed 50 days this school year, and Madysen has missed 30 days.
"From a medical standpoint, they're doing good," Suzy Fitterer said. "It's a double-edged sword. In a lot of ways they're getting better, but as they get bigger so do the problems."
Abygail and Madysen Fitterer have been diagnosed with moderate asthma and celiac disease, and their growth and other physical development were delayed.
The Fitterers are expecting surgeries in the girls' future, including a surgery to construct something to protect their hearts, where the sternum should be, once they finish growing.
"It's just a matter of how many and for what," Stacy Fitterer said. "It's a mystery how they will develop."
They are also concerned about respiratory infections because they suspect the girls' have weaker immune systems.
"Every time they get a cold you worry that it's going to balloon into something else," said Suzy Fitterer, adding that they're prepared to handle the future.
"I know we will have many more trips to Rochester, but that's OK," Suzy Fitterer said. "That's part of the package. I think God has great plans for them."
(Reach Karee Magee at 701-250-8251 or firstname.lastname@example.org.)