Last Updated Aug 27, 2015 4:54 PM EDT
AURORA, Colo. -- A woman who gave birth to conjoined twins at a Denver-area hospital says one of the babies has survived.
Amber McCullough delivered the twin girls, Hannah and Olivia, by cesarean section on Wednesday at the Colorado Fetal Care Center at Children's Hospital Colorado, the hospital said in a statement.
"Because of how the babies were conjoined and the severity of their heart condition, immediate separation was necessary. A multidisciplinary team performed a 5-hour separation procedure," the hospital said.
"I would like everyone to know, and for the message to be read that Hannah did survive the surgery. However, she is very critical and very delicate," McCullough, a Minnesota native, told KARE-TV in Minneapolis.
As doctors expected, the other twin, Olivia, did not survive.
The twins shared an abdomen, liver and intestinal tract. The girls had separate hearts and kidneys, but Olivia's heart had only a single ventricle and was missing valves.
The hospital said the girls' mother is recovering without complication. In the statement, McCullough said, "I believe in the power of prayer and the talent of the medical professionals here." She asked for prayers and privacy.
McCullough chronicled her pregnancy with the twins online, writing on her Facebook page earlier this month, "We are embarking on a new future with much happiness, love, and sorrow."
Because of the way the twins were attached, and the differences in their physical conditions, doctors were expected to try to save Hannah using a surgery called an EXIT procedure -- Ex Utero Intrapartum Treatment -- before cutting the umbilical cord. They would then separate the conjoined twins immediately.
Conjoined twins happen once every 200,000 live births, according to the University of Maryland Medical Center, which says between 40 to 60 percent arrive stillborn.
McCullough, who also has 6-year-old son, is divorced and became pregnant with the twins during another relationship. It wasn't until her second trimester that she learned she was carrying conjoined twins. The relationship with the girls' father ended shortly thereafter.
McCullough said she spent eight years in the U.S. Army, then went to law school and is now an attorney.
She has lived at the Ronald McDonald House in Aurora, near Children's Hospital Colorado, since early August. Her stepmother is there, keeping her company and caring for her, and her son is expected to move there to be with her soon.