• Maggie Altobelli was 20-weeks pregnant when she and her husband learnt that their twins were connected at the abdomen
  • More than two dozen medical specialists were part of the surgery, which took nearly 10 hours to complete
  • Before the surgery, the twins spent nearly a year in the intensive care

Conjoined twins who shared a liver, diaphragm, chest, and abdominal wall have been successfully separated after a surgery in Philadelphia. The 11-month-old girls Addy and Lilianna Altobelli underwent the procedure at Children's Hospital of Philadelphia.

Maggie Altobelli was 20-weeks pregnant when she and her husband Dom learnt that their twins were connected at the abdomen. After being born, the conjoined twins spent nearly a year in intensive care before doctors carried out the surgery, Today reported.

"I was trying to find out the gender of one baby I thought we were having, and then it turned out to be a little more complicated," Maddie told the outlet. "It was an out-of-body experience."

More than two dozen medical specialists were part of the surgery, which took nearly 10 hours to complete. Following the surgery, the children were assisted and medical staff worked to rebuild their chest and abdomen.

Dr Holly Hendrick, the lead surgeon, said that no two surgeries to separate conjoined twins are alike, and that each has its own challenges.

“Separating conjoined twins is always a challenge because every single set of twins is unique, and they all have different challenges and anatomic considerations,” she said in a press statement. “The way our team works together, it’s really incredible and special, with so many people coming together to work toward a common goal. Addy and Lily are doing well, and our hope is that they have full lives that are joyful.”

According to the Mayo Clinic, conjoined twins are born when the embryo fails to fully separate to form two individuals. In most cases, the twins are connected at the chest, pelvis or abdomen. However, in some cases, they may share one or more internal organs as well. Conjoined twins are rare, only appearing in about 1 in 50,000 births.

The surgeons in this case could not immediately operate on the children as they had to wait for the twins’ health to stabilize and for them to grow enough skin to eventually cover the spots were they joined.

"Their shared liver was also large enough to divide between them, making them excellent candidates for separation surgery," Children's Hospital of Philadelphia, where the surgery was performed, said in a statement, according to People.

A week before the surgery, Maggie wrote an emotional letter to her girls.

"Throughout my time here at the place you were born, your Dad and I have witnessed something special — being parents to two miracles," she wrote in the letter, which was shared with Today. "Now to think soon you could become two separate girls is overwhelmingly indescribable."

"On October 13th, as your care team prepares to perform this high-risk surgery on the two of you — know that I am honored to have been chosen to be your mother," she added. "You two are truly remarkable and have changed my life. We are so grateful that God chose us to take you on this journey and get you where you need to go."

While the surgery was successful, Addy and Lily – now 14 months – both still use feeding tubes and ventilators to help with their breathing, the hospital reportedly said.

"They sit up and look at each other and smile and play," Dom, their father, told Today. "Anytime they're close they're reaching for each other's hands and faces and breathing tubes."

Conjoined twins form when an embryo only partially separates into two and the babies develop connected to each other by the abdomen, chest, pelvis, spine or head. Public domain