The operation at The Children's Hospital of Philadelphia took surgeons 11 hours, and the sisters are now recovering in in intensive care.
“This past week has been one of the most intense weeks of my entire life. It included being excited, nervous, terrified, relieved, worried, stressed, tired, overjoyed, overwhelmed, and curious,” Erin and Abby's mum Heather shared on her blog.
Heather received hourly updates on the operation, but was first focused on Abby as she had a greater risk of dying during the surgery.
"My mind immediately went to Abby. My heart ached and all I wanted to do was be able to hold their hands and tell them that they could do it. That they would make it through the surgery," she wrote.
Abby did lose a lot of blood, but thankfully both girls survived.
"At that moment I stood in the middle of the room in-between two beds and realised what had happened. We had two girls. Two separate girls independent of each other."
This article was first published on New Idea.